Movable body drive method and movable body drive system, pattern formation method and apparatus, exposure method and apparatus, and device manufacturing method

ABSTRACT

During the drive of a stage, positional information in a movement plane of a stage is measured by three encoders that include at least one each of an X encoder and a Y encoder of an encoder system, and a controller switches an encoder used for a measurement of positional information of a stage in the movement plane from an encoder to an encoder so that the position of the stage in the movement plane is maintained before and after the switching. Therefore, although the switching of the encoder used for controlling the position of the stage is performed, the position of the stage in the movement plane is maintained before and after the switching, and a correct linkage becomes possible.

This is a continuation of U.S. application Ser. No. 11/896,448 filedAug. 31, 2007, which claims priority to Japanese Application No.2006-237045 filed on Aug. 31, 2006, Japanese Application No. 2006-237491filed on Sep. 1, 2006 and Japanese Application No. 2006-237606 filed onSep. 1, 2006. The entire disclosures of the prior applications arehereby incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to movable body drive methods and movablebody drive systems, pattern formation methods and apparatuses, exposuremethods and apparatuses, and device manufacturing methods, and moreparticularly to a movable body drive method in which a movable body isdriven within a movement plane and a movable body drive system, apattern formation method using the movable body drive method and apattern formation apparatus equipped with the movable body drive system,an exposure method using the movable body drive method and an exposureapparatus equipped with the movable body drive system, and a devicemanufacturing method in which the pattern formation method is used.

2. Description of the Background Art

Conventionally, in a lithography process for manufacturing microdevices(electron devices and the like) such as semiconductor devices and liquidcrystal display devices, exposure apparatuses such as a projectionexposure apparatus by a step-and-repeat method (a so-called stepper) anda projection exposure apparatus by a step-and-scan method (a so-calledscanning stepper (which is also called a scanner) are relativelyfrequently used.

In this kind of exposure apparatus, in order to transfer a pattern of areticle (or a mask) on a plurality of shot areas on a wafer, a waferstage holding the wafer is driven in an XY two-dimensional direction,for example, by linear motors and the like. Especially in the case of ascanning stepper, not only the wafer stage but also a reticle stage isdriven in by predetermined strokes in a scanning direction by linearmotors and the like. Position measurement of the reticle stage and thewafer stage is generally performed using a laser interferometer whosestability of measurement values is good for over a long time and has ahigh resolution.

However, requirements for a stage position control with higher precisionare increasing due to finer patterns that accompany higher integrationof semiconductor devices, and now, short-term variation of measurementvalues due to temperature fluctuation of the atmosphere on the beamoptical path of the laser interferometer has come to occupy a largepercentage in the overlay budget.

Meanwhile, as a measurement unit besides the laser interferometer usedfor position measurement of the stage, an encoder can be used, however,because the encoder uses a scale, which lacks in mechanical long-termstability (drift of grating pitch, fixed position drift, thermalexpansion and the like), it makes the encoder have a drawback of lackingmeasurement value linearity and being inferior in long-term stabilitywhen compared with the laser interferometer.

In view of the drawbacks of the laser interferometer and the encoderdescribed above, various proposals are being made (refer to Kokai(Japanese Patent Unexamined Application Publication) No. 2002-151405,Kokai (Japanese Patent Unexamined Application Publication) No.2004-101362 and the like) of a unit that measures the position of astage using both a laser interferometer and an encoder (a positiondetection sensor which uses a diffraction grating) together.

Further, the measurement resolution of the conventional encoder wasinferior when compared with an interferometer, however, recently, anencoder which has a nearly equal or a better measurement resolution thana laser interferometer has appeared (for example, refer to Kokai(Japanese Patent Unexamined Application Publication) No. 2005-308592),and the technology to put the laser interferometer and the encoderdescribed above together is beginning to gather attention.

However, in the case position measurement is performed of the movementplane of the wafer stage of the exposure apparatus that movestwo-dimensionally holding a wafer using an encoder, for example, inorder to avoid an unnecessary increase in the size of the wafer stageand the like, it becomes essential to switch the encoder used forcontrol while the wafer stage is moving using a plurality of encoders,or in other words, to perform a linkage between the plurality ofencoders. However, as it can be easily imagined, for example, whenconsidering the case when a grating is placed on the wafer stage, it isnot so easy to perform linkage between a plurality of encoders while thewafer stage is being moved, especially while precisely the wafer stageis being moved two-dimensionally along a predetermined path.

Further, by repeating the linkage operation, the position error of thewafer stage may grow large with the elapse of time due to theaccumulation of the error which occurs when linkage is performed, andthe exposure accuracy (overlay accuracy) may consequently deteriorate.

Meanwhile, it is conceivable that the position of the wafer stage doesnot necessarily have to be measured using an encoder system in the wholemovable range of the wafer stage.

Now, the propagation speed in the cable of an electrical signal such asthe detection signal of the head of the encoder, or more specifically,the photoelectric conversion signal of the light receiving element islimited, and the length of the cable through which the detection signalof the encoder propagates is generally from several meters to 10 m, andin quite a few cases exceeds 10 m. When considering that a signalpropagates through the cable of such a length at the speed of light, theinfluence of the delay time that accompanies the propagation is at alevel that cannot be ignored.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of thecircumstances described above, and according to the first aspect of thepresent invention, there is provided a first movable body drive methodin which a movable body is driven in a movement plane including a firstaxis and a second axis orthogonal to each other, the method comprising:a measuring process in which positional information of the movable bodyin the movement plane is measured using at least one encoder of anencoder system including a plurality of encoders having a head thatirradiates a detection light on a grating and receives the detectionlight from the grating; and a switching process in which at least one ofan encoder used for position control of the movable body is switched toanother encoder so as to maintain a position of the movable body in themovement plane before and after the switching.

According to this method, while the movable body is driven, positionalinformation of the movable body in the movement plane is measured usingat least two encoders of the encoder system, and the encoder used forposition control of the movable body is switched from at least one of anencoder used for position control of the movable body to another encoderso as to maintain the position of the movable body in the movement planebefore and after the switching. Therefore, although the switching of theencoder used for the control of the position of the movable body isperformed, the position of the movable body in the movement plane ismaintained before and after the switching, and a precise linkage becomespossible. Accordingly, it becomes possible to move the movable bodytwo-dimensionally precisely along a predetermined course, whileperforming the linkage between a plurality of encoders.

According to the second aspect of the present invention, there isprovided a second movable body drive method in which a movable body isdriven in a movement plane, the method comprising: an intake process inwhich measurement data corresponding to a detection signal of at leastone head of an encoder system including a plurality of heads thatmeasure positional information of the movable body within the movementplane is taken in at a predetermined control sampling interval when themovable body is driven in a predetermined direction in the movementplane; and a drive process in which the movable body is driven so as tocorrect a measurement error of the head due to a measurement delay thataccompanies propagation of the detection signal, based on a plurality ofdata which include the most recent measurement data that was taken inthe latest and previous measurement data including at least data justbefore the most recent measurement data, and information of a delay timethat accompanies propagation of the detection signal through apropagation path.

According to this method, when the movable body is driven in apredetermined direction in the movement plane, measurement datacorresponding to the detection signal of at least one head of an encodersystem which measures positional information of the movable body in themovement plane are taken in at a predetermined control samplinginterval, and the movable body is driven so that a measurement error ofthe head due to a measurement delay that accompanies the propagation ofthe detection signal is corrected drives movable body so that it iscorrected, based on a plurality of data including the most recentmeasurement data taken in the latest and previous data including atleast data just before the most recent measurement data (one controlsampling interval earlier), and information of a delay time thataccompanies propagation of the detection signal through a propagationpath. Accordingly, it becomes possible to drive movable body with highprecision in the desired direction, without being affected by themeasurement delay that accompanies the propagation of the detectionsignal of the head of the encoder through the propagation path.

According to the third aspect of the present invention, there isprovided a pattern formation method, comprising: a mount process inwhich an object is mounted on a movable body that can move in a movementplane; and a drive process in which the movable body is driven by themovable body drive method according to one of the first and secondmovable body drive methods, to form a pattern on the object.

According to this method, by forming a pattern on the object mounted onthe movable body which is driven using one of the first and secondmovable body drive methods of the present invention, it becomes possibleto form a desired pattern on the object.

According to a fourth aspect of the present invention, there is provideda first device manufacturing method including a pattern formationprocess wherein in the pattern formation process, a pattern is formed ona substrate using the pattern formation method according to the patternformation method of the present invention.

According to a fifth aspect of the present invention, there is provideda first exposure method in which a pattern is formed on an object by anirradiation of an energy beam wherein for relative movement of theenergy beam and the object, a movable body on which the object ismounted is driven, using one of the first and second movable body drivesmethod of the present invention.

According to this method, for relative movement of the energy beamirradiated on the object and the object, the movable body on which theobject is mounted is driven with good precision, using one of the firstand second movable body drive methods of the present invention.Accordingly, it becomes possible to form a desired pattern on the objectby scanning exposure.

According to a sixth aspect of the present invention, there is provideda second exposure method in which an object on a movable body that movesin a movement plane is sequentially exchanged, and a pattern is formedrespectively on each object by sequentially exposing the object afterexchange, wherein each time the exchange of the object is performed onthe movable body, position control of the movable body in the movementplane is started once more, using at least three encoders of an encodersystem that measures positional information of the movable body in themovement plane within a predetermined effective area including anexposure position.

According to this method, each time the exchange of the object isperformed on the movable body, position control of the movable body inthe movement plane using at least three encoders of an encoder systemthat measures positional information of the movable body in the movementplane in an effective area is started once more. Therefore, each timethe object exchange is performed, the position error of the movable bodyis canceled out, so that the position error of the movable body does notincrease with the passage of time. Accordingly, it becomes possible tomeasure the positional information of the movable body in the movementplane in a predetermined effective area including the exposure positionby the encoder system with good precision for over a long time, whichmakes it possible to maintain the exposure precision for over a longperiod of time.

According to a seventh aspect of the present invention, there isprovided a third movable body drive method in which a movable body isdriven in a movement plane, the method comprising: an execution processin which of an encoder system including a plurality of encodersrespectively having a head that irradiates a detection light on agrating and receives the detection light from the grating and measurespositional information of the movable body in the movable plane, anoutput of each encoder is constantly taken in, and an operation ofswitching an encoder used for position control of the movable body froman encoder that has been used for position control of the movable bodyto another encoder, at a timing in synchronization with the positioncontrol of the movable body is executed.

According to this method, when the movable body is driven, the output ofeach encoder of the encoder system is constantly taken in, and anoperation of switching an encoder used for the position control of themovable body from an encoder that has been used for position control ofthe movable body to another encoder is executed at a timing insynchronization with the position control of the movable body.Therefore, the switching of the encoder will not have to be performed ata high speed, and a highly precise hardware for the switching will notbe necessary, which consequently will make cost reduction possible.

According to an eighth aspect of the present invention, there isprovided a fourth movable body drive method in which a movable body isdriven in a movement plane including a first axis and a second axisorthogonal to each other, the method comprising: a measuring process inwhich positional information of the movable body in the movement planeis measured using at least one encoder of an encoder system including aplurality of encoders respectively having a head that irradiates adetection light on a grating and receives the detection light from thegrating; a scheduling process in which a combination of encoders subjectto a switching where an encoder used for position control of the movablebody is switched from an arbitrary encoder to another encoder is madeand a switching timing is prepared, based on a movement course of themovable body; and a switching process in which the arbitrary encoder isswitched to the another encoder based on the contents prepared in thescheduling.

According to this method, a combination of encoders subject to aswitching where an encoder used for position control of the movable bodyis switched from an arbitrary encoder to another encoder is made and aswitching timing is prepared, based on a movement course of the movablebody. And when the movable body is moving, the positional information ofthe movable body in the movement plane is measured using at least oneencoder of the encoder system, and based on the contents made out in thescheduling above, the switching from an arbitrary encoder to anotherencoder is performed. According to this, a reasonable encoder switchingaccording to the target track of the movable body becomes possible.

According to a ninth aspect of the present invention, there is provideda first movable body drive system in which a movable body is driven in amovement plane including a first axis and a second axis orthogonal toeach other, the system comprising: an encoder system having a pluralityof encoders respectively having a head that irradiates a detection lighton a grating and receives the detection light from the grating,including a first encoder used for measuring positional information ofthe movable body in a direction parallel to the first axis; and acontroller that measures positional information of the movable body inthe movement plane using at least one encoder of the encoder system, andalso switches at least one of an encoder used for measurement of thepositional information of the movable body in the movement plane toanother encoder so as to maintain a position of the movable body in themovement plane before and after the switching.

According to this system, when the movable body is driven, thepositional information of the movable body in the movement plane ismeasured by at least two encoders which at least includes include oneeach of the first encoder and the second encoder of the encoder system,and the controller switches the encoder used for measurement of thepositional information of the movable body in the movement plane from anencoder of either of the at least two encoders to another encoder sothat the position of the movable body in the movement plane ismaintained before and after the switching. Therefore, although theswitching of the encoder used for controlling the position of themovable body is performed, the position of the movable body in themovement plane is maintained before and after the switching, whichallows an accurate linkage. Accordingly, it becomes possible to move themovable body two-dimensionally, precisely along a predetermined course,while performing linkage between a plurality of encoders.

According to a tenth aspect of the present invention, there is provideda second movable body drive system in which a movable body is driven ina movement plane, the system comprising: an encoder system including aplurality of heads that measure positional information of the movablebody in the movement plane; and a controller that takes in measurementdata corresponding to a detection signal of at least one head of anencoder system at a predetermined control sampling interval when themovable body is driven in a predetermined direction in the movementplane, and drives the movable body so that the measurement error of thehead due to a measurement delay that accompanies propagation of thedetection signal is corrected, based on a plurality of data that includethe most recent measurement data that was taken in the latest andprevious measurement data including at least data just before the mostrecent measurement data, and information of a delay time thataccompanies propagation of the detection signal through a propagationpath.

According to this system, when the movable body is driven by thecontroller in a predetermined direction in the movement plane, themeasurement data corresponding to the detection signal of at least onehead of the encoder system are taken in at a predetermined controlsampling interval, and the movable body is driven so as to correct themeasurement error of the head due to a measurement delay thataccompanies propagation of the detection signal, based on a plurality ofdata that include the most recent measurement data that was taken in thelatest and previous measurement data including at least data just beforethe most recent measurement data, and information of a delay time thataccompanies propagation of the detection signal through a propagationpath. According to this, it becomes possible to drive the movable bodywith high precision in the desired direction without being affected bythe measurement delay that accompanies the detection signals of the headof the encoder propagating through the propagation path.

According to an eleventh aspect of the present invention, there isprovided a third movable body drive system in which a movable body isdriven in a movement plane, the system comprising: an encoder systemincluding a plurality of heads that measure positional information ofthe movable body in the movement plane; an interferometer system thatmeasures positional information of the movable body in the movementplane; a processing unit that executes a delay time acquisitionprocessing of driving the movable body in a predetermined direction,taking in a detection signal of each head and a detection signal of theinterferometer system simultaneously at a predetermined sampling timingfor a plurality of heads of the encoder system during the drive, andbased on both detection signals, acquiring information of the delay timeof the detection signals of the respective plurality of heads thataccompanies the propagation through the propagation path, with thedetection signal of the interferometer system serving as a reference;and a controller that drives the movable body, based on measurement datacorresponding to the respective detection signals of the plurality ofheads of the encoder system and information of a delay time of theplurality of heads, respectively.

According to this system, the processing unit executes a delay timeacquisition process in which a delay time acquisition processing ofdriving the movable body in a predetermined direction, taking in adetection signal of each head and a detection signal of theinterferometer system simultaneously at a predetermined sampling timingfor at least a plurality of heads of the encoder system during thedrive, and based on both detection signals, acquiring information of thedelay time of the detection signals of the respective plurality of headsthat accompanies the propagation through the propagation path, with thedetection signal of the interferometer system serving as a reference areexecuted. Accordingly, it becomes possible for the processing unititself to obtain information of the delay time on each of the pluralityof heads with the detection signal of the interferometer system servingas a reference. Then, the controller drives the movable body based onthe measurement data corresponding to each detection signal of theplurality of heads of the encoder system and information of the delaytime for each of the plurality of heads that has been obtained.Accordingly, even if the delay time is different for each head, itbecomes possible to drive the movable body using each encoder of theencoder system with good precision, without being affected by thedifference of the delay time between the plurality of heads.

According to a twelfth aspect of the present invention, there isprovided a first pattern formation apparatus, the apparatus comprising:a movable body on which an object is mounted, and is movable in amovement plane holding the object; and a movable body drive systemaccording to any one of the first to third movable body drive systems ofthe present invention that drives the movable body to perform patternformation with respect to the object.

According to this apparatus, by generating a pattern on an object on themovable body driven by any one of the first to third movable body drivesystems of the present invention with a patterning unit, it becomespossible to form a desired pattern on the object.

According to a thirteenth aspect of the present invention, there isprovided a first exposure apparatus that forms a pattern on an object byan irradiation of an energy beam, the apparatus comprising: a patterningunit that irradiates the energy beam on the object; and the movable bodydrive system according to any one of the first to third movable bodydrive systems of the present invention, wherein the movable body drivesystem drives the movable body on which the object is mounted forrelative movement of the energy beam and the object.

According to this apparatus, for relative movement of the energy beamirradiated on the object from the patterning unit and the object, themovable body on which the object is mounted is driven by any one of thefirst to third movable body drive system of the present invention.Accordingly, it becomes possible to form a desired pattern on the objectby scanning exposure.

According to a fourteenth aspect of the present invention, there isprovided a second exposure apparatus that sequentially exchanges anobject on a movable body that moves in a movement plane, and forms apattern respectively on each object by sequentially exposing the objectafter exchange, the apparatus comprising: an encoder system including atleast three encoders that measure positional information of the movablebody in the movement plane in a predetermined effective area includingan exposure position; and a controller that starts position control ofthe movable body in the movement plane using at least the three encodersof the encoder system once more, each time exchange of the object isperformed on the movable body.

According to this apparatus, each time the exchange of the object isperformed on the movable body by the controller, position control of themovable body in the movement plane using at least three encoders of anencoder system that measure positional information in the movement planeof the movable body in the effective area is started once more.Therefore, each time the object exchange is performed, the positionerror of the movable body is canceled out, so that the position error ofthe movable body does not increase with the passage of time.Accordingly, it becomes possible to measure the positional informationof the movable body in the movement plane in a predetermined effectivearea including the exposure position by the encoder system with goodprecision for over a long time, which makes it possible to maintain theexposure precision for over a long period of time.

According to a fifteenth aspect of the present invention, there isprovided a fourth movable body drive system in which a movable body isdriven in a movement plane, the system comprising: an encoder systemincluding a plurality of encoders respectively having a head thatirradiates a detection light on a grating and receives the detectionlight from the grating and measures positional information of themovable body in the movable plane; and a controller that constantlytakes in an output of each encoder of the encoder system, and alsoexecutes an operation to switch the encoder used for control of themovable body from an encoder that has been used for position control ofthe movable body to another encoder in synchronization with the timingof the position control of the movable body.

According to the system, when the movable body is driven, the controllerconstantly takes in the output of each encoder of the encoder system,and executes an operation of switching an encoder used for positioncontrol of the movable body from an encoder that has been used forposition control of the movable body to another encoder at a timing insynchronization with the position control of the movable body.Therefore, the switching of the encoder will not have to be performed ata high speed, and a highly precise hardware for the switching will notbe necessary, which consequently will make cost reduction possible.

According to a sixteenth aspect of the present invention, there isprovided a fifth movable body drive system in which a movable body isdriven in a movement plane including a first axis and a second axisorthogonal to each other, the system comprising: an encoder systemincluding a plurality of encoders having a head that irradiates adetection light on a grating and receives the detection light from thegrating and measures positional information of the movable body in themovable plane; and a controller that makes a combination of encoderssubject to a switching where an encoder used for position control of themovable body is switched from an arbitrary encoder to another encoderand prepares a switching timing, based on a movement course of themovable body.

According to this system, the controller makes a combination of encoderssubject to a switching where an encoder used for position control of themovable body is switched from an arbitrary encoder to another encoderand prepares a switching timing, based on a movement course of themovable body. And when the movable body is moving, the positionalinformation of the movable body in the movement plane is measured usingat least one encoder of the encoder system, and based on the contentsmade out in the scheduling above, the switching from an arbitraryencoder to another encoder is performed. According to this, a reasonableencoder switching according to the target track of the movable bodybecomes possible.

According to a seventeenth aspect of the present invention, there isprovided a second pattern formation apparatus, the apparatus comprising:a movable body on which the object is mounted, and is movable in amovement plane holding the object; and a movable body drive systemaccording to one of the fourth and fifth movable body drive systems ofthe present invention that drives the movable body to perform patternformation with respect to the object.

According to this apparatus, by generating a pattern on the object onthe movable body driven smoothly by one of the fourth and fifth movablebody drive systems of the present invention with a patterning unit, itbecomes possible to form a pattern on the object with good precision.

According to an eighteenth aspect of the present invention, there isprovided a third exposure apparatus that forms a pattern on an object byan irradiation of an energy beam, the apparatus comprising: a patterningunit that irradiates the energy beam on the object; and the movable bodydrive system according to one of the fourth and fifth movable body drivesystems of the present invention, wherein the movable body drive systemdrives the movable body on which the object is mounted for relativemovement of the energy beam and the object.

According to this apparatus, for relative movement of the energy beamirradiated on the object from the patterning unit and the object, themovable body on which the object is mounted is driven with goodprecision by one of the fourth and fifth movable body drive system ofthe present invention. Accordingly, it becomes possible to form apattern on the object with good precision by scanning exposure.

According to a nineteenth aspect of the present invention, there isprovided a fourth exposure apparatus that exposes an object with anenergy beam, the apparatus comprising: a movable body that holds theobject and is movable at least in a first and second directions whichare orthogonal in a predetermined plane; an encoder system in which oneof a grating section and a head unit is arranged on a surface of themovable body where the object is held and the other is arranged facingthe surface of the movable body, and positional information of themovable body in the predetermined plane is measured by a head that facesthe grating section of a plurality of heads of the head unit; and acontroller that decides the positional information which should bemeasured by a head after a switching, during the switching of the headused for the measurement that accompanies the movement of the movablebody, based on positional information measured by a head before theswitching and positional information of the movable body in a directiondifferent from the first and second directions.

According to the apparatus, before and after the switching of the headused for position measurement of the movable body that accompanies themovement of the movable body, the position of the movable body ismaintained, which allows a smooth switching of the head. Accordingly, itbecomes possible to drive the movable body two-dimensionally accuratelyat least within the predetermined plane, while performing switchingbetween a plurality of heads, which in turn allows exposure of theobject on the movable body to be performed with good precision.

According to a twentieth aspect of the present invention, there isprovided a fifth exposure apparatus that exposes an object with anenergy beam, the apparatus comprising: a movable body that holds theobject and is movable at least in a first and second directions whichare orthogonal in a predetermined plane; an encoder system in which oneof a grating section and a head unit is arranged on a surface of themovable body where the object is held and the other is arranged facingthe surface of the movable body, and positional information of themovable body in the predetermined plane is measured by a head that facesthe grating section of a plurality of heads of the head unit; and acontroller that continues the measurement while switching the head usedfor the measurement to another head during the movement of the movablebody, and controls a position of the movable body in the predeterminedplane, based on measurement information of the encoder system measuredby the another head and positional information of the movable body in adirection different from the first and second directions on theswitching.

According to this, it becomes possible to drive the movable bodytwo-dimensionally accurately at least within the predetermined plane,while performing switching between a plurality of heads, which in turnallows exposure of the object on the movable body to be performed withgood precision.

According to a twenty-first aspect of the present invention, there isprovided a sixth exposure apparatus that exposes an object with anenergy beam, the apparatus comprising: a movable body that holds theobject and is movable at least in a first and second directions whichare orthogonal in a predetermined plane; an encoder system in which oneof a grating section and a head unit is arranged on a surface of themovable body where the object is held and the other is arranged facingthe surface of the movable body, and positional information of themovable body in the first and second directions, and rotationaldirection in the predetermined plane is measured by at least three headsthat face the grating section of a plurality of heads of the head unit;and a controller that continues the measurement while switching thethree heads used for the measurement to three heads having at least onedifferent head during the movement of the movable body, and during theswitching, decides position information that should be measured by atleast one head of the three heads after the switching which aredifferent from the three heads before the switching, based on positionalinformation measured by the three heads before the switching.

According to the apparatus, before and after the switching of the headused for position measurement of the movable body that accompanies themovement of the movable body, the position (including rotation in thepredetermined plane) of the movable body is maintained, which allows asmooth switching of the head. Accordingly, it becomes possible to drivethe movable body two-dimensionally accurately at least within thepredetermined plane, while performing switching between a plurality ofheads, which in turn allows exposure of the object on the movable bodyto be performed with good precision.

According to a twenty-second aspect of the present invention, there isprovided a seventh exposure apparatus that exposes an object with anenergy beam, the apparatus comprising: a movable body that holds theobject and is movable at least in a first and second directions whichare orthogonal in a predetermined plane; an encoder system in which oneof a grating section and a head unit is arranged on a surface of themovable body where the object is held and the other is arranged facingthe surface of the movable body, and positional information of themovable body in the predetermined plane is measured by a head that facesthe grating section of a plurality of heads of the head unit; and acontroller that controls a position of the movable body in thepredetermined plane, based on positional information of the head usedfor measuring the positional information in a surface parallel to thepredetermined plane and measurement information of the encoder system.

According to the apparatus, it becomes possible to drive the movablebody two-dimensionally accurately at least within the predeterminedplane, which in turn allows exposure of the object on the movable bodyto be performed with good precision, without being affected by themeasurement error of the encoder system due to the shift (for example,shift from the design position) of position of the head used for themeasurement of the positional information in a surface parallel to thepredetermined plane.

According to a twenty-third aspect of the present invention, there isprovided an eighth exposure apparatus that exposes an object with anenergy beam, the apparatus comprising: a movable body that holds theobject and is movable at least in a first and second directions whichare orthogonal in a predetermined plane; an encoder system in which oneof a grating section and a head unit is arranged on a surface of themovable body where the object is held and the other is arranged facingthe surface of the movable body, and positional information of themovable body in the predetermined plane is measured by a head that facesthe grating section of a plurality of heads of the head unit; and acontroller that measures positional information of the plurality ofheads of the head unit in a surface parallel to the predetermined planeand controls a position of the movable body in the predetermined plane,based on positional information that has been measured and measurementinformation of the encoder system.

According to the apparatus, it becomes possible to drive the movablebody two-dimensionally accurately at least within the predeterminedplane, which in turn allows exposure of the object on the movable bodyto be performed with good precision. According to a twenty-fourth aspectof the present invention, there is provided third exposure method ofexposing an object with an energy beam wherein the object is mounted ona movable body that can move in at least a first and second directionwhich are orthogonal in a predetermined plane, whereby positionalinformation of the movable body is measured using an encoder system inwhich one of a grating section and a head unit is arranged on a surfaceof the movable body where the object is mounted and the other isarranged facing the surface of the movable body, and positionalinformation of the movable body in the predetermined plane is measuredby a head that faces the grating section of a plurality of heads of thehead unit, and the positional information which should be measured by ahead after a switching during the switching of the head used for themeasurement that accompanies the movement of the movable body isdecided, based on positional information measured by a head before theswitching and positional information of the movable body in a directiondifferent from the first and second directions.

According to this method, before and after the switching of the headused for position measurement of the movable body that accompanies themovement of the movable body, the position of the movable body ismaintained, which allows a smooth switching of the head. Accordingly, itbecomes possible to drive the movable body two-dimensionally accuratelyat least within the predetermined plane, while performing switchingbetween a plurality of heads, which in turn allows exposure of theobject on the movable body to be performed with good precision.

According to a twenty-fifth aspect of the present invention, there isprovided a fourth exposure method of exposing an object with an energybeam wherein the object is mounted on a movable body that can move in atleast a first and second direction which are orthogonal in apredetermined plane, whereby positional information of the movable bodyis measured using an encoder system in which one of a grating sectionand a head unit is arranged on a surface of the movable body where theobject is mounted and the other is arranged facing the surface of themovable body, and positional information of the movable body in thepredetermined plane is measured by a head that faces the grating sectionof a plurality of heads of the head unit, and the measurement iscontinued while switching the head used for the measurement to anotherhead during the movement of the movable body, and a position of themovable body in the predetermined plane is controlled based onmeasurement information of the encoder system measured by the anotherhead and positional information of the movable body in a directiondifferent from the first and second directions on the switching.

According to the method, it becomes possible to drive the movable bodytwo-dimensionally accurately at least within the predetermined plane,while performing switching between a plurality of heads, which in turnallows exposure of the object on the movable body to be performed withgood precision. According to a twenty-sixth aspect of the presentinvention, there is provided a fifth exposure method of exposing anobject with an energy beam wherein the object is mounted on a movablebody that can move in at least a first and second direction which areorthogonal in a predetermined plane, whereby positional information ofthe movement body is measured using an encoder system in which one of agrating section and a head unit is arranged on a surface of the movablebody where the object is held and the other is arranged facing thesurface of the movable body and which also measures positionalinformation of the movable body in the first direction, the seconddirection, and rotational direction in the predetermined plane with atleast three heads that face the grating section of a plurality of headsof the head unit, and the measurement is continued while switching thethree heads used for the measurement to three heads having at least onedifferent head during the movement of the movable body, and during theswitching, position information that should be measured by at least onehead of the three heads after the switching which are different from thethree heads before the switching is decided, based on positionalinformation measured by the three heads before the switching.

According to this method, before and after the switching of the headused for position measurement of the movable body that accompanies themovement of the movable body, the position (including rotation in thepredetermined plane) of the movable body is maintained, which allows asmooth switching of the head. Accordingly, it becomes possible to drivethe movable body two-dimensionally accurately at least within thepredetermined plane, while performing switching between a plurality ofheads, which in turn allows exposure of the object on the movable bodyto be performed with good precision.

According to a twenty-seventh aspect of the present invention, there isprovided a sixth exposure method of exposing an object with an energybeam wherein the object is mounted on a movable body that can move in atleast a first and second direction which are orthogonal in apredetermined plane, whereby one of a grating section and a head unit isarranged on a surface of the movable body where the object is held andthe other is arranged facing the surface of the movable body, and theposition of the movable body in the predetermined plane is controlled,based on measurement information of an encoder system that measurespositional information of the movable body in the predetermined plane bya head that faces the grating section of a plurality of heads of thehead unit, and positional information of the head used to measure thepositional information in a surface parallel to the predetermined plane.

According to the method, it becomes possible to drive the movable bodytwo-dimensionally accurately at least within the predetermined plane,which in turn allows exposure of the object on the movable body to beperformed with good precision, without being affected by the measurementerror of the encoder system due to the shift (for example, shift fromthe design position) of position of the head used for the measurement ofthe positional information in a surface parallel to the predeterminedplane.

According to a twenty-eighth aspect of the present invention, there isprovided a seventh exposure method of exposing an object with an energybeam wherein the object is mounted on a movable body that can move in atleast a first and second direction which are orthogonal in apredetermined plane, whereby of an encoder system in which one of agrating section and a head unit is arranged on a surface of the movablebody where the object is held and the other is arranged facing thesurface of the movable body, and positional information of the movablebody in the predetermined plane is measured by a head that faces thegrating section of a plurality of heads of the head unit, the positionalinformation of a plurality of heads of the head unit in a surfaceparallel to the predetermined plane is measured, and based on measuredpositional information and the measurement information of the encodersystem, the position of the movable body in the predetermined plane iscontrolled.

According to the method, it becomes possible to drive the movable bodytwo-dimensionally accurately at least within the predetermined plane,which in turn allows exposure of the object on the movable body to beperformed with good precision.

According to a twenty-ninth aspect of the present invention, there isprovided a second device manufacturing method including a lithographyprocess wherein in the lithography process, a sensitive object mountedon the movable body is exposed using the exposure method according toone of the third and seventh exposure method of the present invention,and a pattern is formed on the sensitive object.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings;

FIG. 1 is a view schematically showing the configuration of an exposureapparatus related to an embodiment;

FIG. 2 is a planar view showing a stage unit in FIG. 1;

FIG. 3 is a planar view showing the placement of various measuringapparatuses (such as encoders, alignment systems, a multipoint AFsystem, and Z sensors) that are equipped in the exposure apparatus inFIG. 1;

FIG. 4A is a planar view showing a wafer stage, and FIG. 4B is aschematic side view of a partially sectioned wafer stage WST;

FIG. 5A is a planar view showing a measurement stage, and FIG. 5B is aschematic side view showing a partial cross section of the measurementstage;

FIG. 6 is a block diagram showing a main configuration of a controlsystem of the exposure apparatus related to an embodiment;

FIG. 7A is a view showing an example of a configuration of an encoder,and FIG. 7B is a view showing the case when a laser beam LB having asectional shape extending narrowly in the periodic direction of gratingRG is used as a detection light;

FIG. 8A is a view showing a Doppler effect which the light scattered bya movement plane receives, and FIG. 8B is a view for explaining arelation between incoming light and diffraction light with respect to areflection type diffraction grating of a beam in the encoder head;

FIG. 9A is a view showing a case when a measurement value does notchange even if a relative movement in a direction besides themeasurement direction occurs between a head of an encoder and a scale,and FIG. 9B is a view showing a case when a measurement value changeswhen a relative movement in a direction besides the measurementdirection occurs between a head of an encoder and a scale;

FIGS. 10A to 10D are views used for describing the case when themeasurement value of the encoder changes and the case when themeasurement values do not change, when a relative movement in thedirection besides the measurement direction occurs between the head andthe scale;

FIGS. 11A and 11B are views for explaining an operation to acquirecorrection information to correct a measurement error of an encoder (afirst encoder) due to the relative movement of the head and the scale inthe direction besides the measurement direction;

FIG. 12 is a graph showing a measurement error of the encoder withrespect to the change in the Z position in pitching amount θx=α;

FIG. 13 is a view for explaining an operation to acquire correctioninformation to correct a measurement error of another encoder (a secondencoder) due to the relative movement of the head and the scale in thedirection besides the measurement direction;

FIG. 14 is a view for describing a calibration process of a headposition;

FIG. 15 is a view for explaining a calibration process to obtain an Abbeoffset quantity;

FIG. 16 is a view for explaining an inconvenience that occurs in thecase a plurality of measurement points on the same scale is measured bya plurality of heads;

FIG. 17 is a view for explaining a method to measure the unevenness ofthe scale (No. 1);

FIGS. 18A to 18D are views for explaining a method to measure theunevenness of the scale (No. 2);

FIG. 19 is a view for describing an acquisition operation of correctioninformation of the grating pitch of the scale and the correctioninformation of the grating deformation;

FIG. 20 is a view for explaining a method to obtain a delay time thataccompanies a propagation of the detection signal of each Y head througha cable;

FIG. 21 is a view for describing an example of a correction method ofthe measurement error of the encoder due to the measurement delay thataccompanies a propagation of the detection signal of each head through acable;

FIGS. 22A and 22B are views for explaining a concrete method to converta measurement value of the encoder that has been corrected into aposition of wafer stage WST;

FIGS. 23A and 23B are views for describing a carryover of positionmeasurement of the wafer table in the XY plane by a plurality ofencoders which respectively include a plurality of heads placed in theshape of an array and the measurement value between the heads;

FIGS. 24A to 24E are views for explaining a procedure of an encoderswitching;

FIG. 25 is a view for explaining the switching process of the encoderused for position control of the wafer stage in the XY plane;

FIG. 26 is a view conceptually showing position control of the waferstage, intake of the count value of the encoder, and an encoderswitching timing;

FIG. 27 is a view showing a state of the wafer stage and the measurementstage where exposure to a wafer on the wafer stage is performed by astep-and-scan method;

FIG. 28 is a view showing the state of both stages just after the stagesshifted from a state where the wafer stage and the measurements stageare distanced to a state where both stages are in contact after exposurehas been completed;

FIG. 29 is a view showing a state where the measurement stage moves inthe −Y direction and the wafer stage moves toward an unloading position,while maintaining the positional relation between the wafer table andthe measurement table in the Y-axis direction;

FIG. 30 is a view showing a state of the wafer stage and the measurementstage when the measurement stage arrives at a position where Sec-BCHK(an interval) is performed;

FIG. 31 is a view showing a state of the wafer stage and the measurementstage when the wafer stage moves from the unloading position to aloading position, in parallel with the Sec-BCHK (interval) beingperformed;

FIG. 32 is a view showing a state of the wafer stage and the measurementstage when the measurement stage moves to an optimal scrum waitingposition and a wafer is loaded on a wafer table;

FIG. 33 is a view showing a state of both stages when the wafer stagehas moved to a position where the Pri-BCHK former process is performedwhile the measurement stage is waiting at the optimal scrum waitingposition;

FIG. 34 is a view showing a state of the wafer stage and the measurementstage when alignment marks arranged in three first alignment shot areasare being simultaneously detected using alignment systems AL1, AL2₂ andAL2₃;

FIG. 35 is view showing a state with a wafer stage and the measurementstage when the focus calibration former process is performed;

FIG. 36 is a view showing a state of the wafer stage and the measurementstage when alignment marks arranged in five second alignment shot areasare being simultaneously detected using alignment systems AL1 and AL2₁to AL2₄;

FIG. 37 is a view showing a state of the wafer stage and the measurementstage when at least one of the Pri-BCHK latter process and the focuscalibration latter process is being performed;

FIG. 38 is a view showing a state of the wafer stage and the measurementstage when alignment marks arranged in five third alignment shot areasare being simultaneously detected using alignment systems AL1 and AL2₁to AL2₄;

FIG. 39 is a view showing a state of the wafer stage and the measurementstage when alignment marks arranged in three fourth alignment shot areasare being simultaneously detected using alignment systems AL1, AL2₂ andAL2₃;

FIG. 40 is a view showing a state of the wafer stage and the measurementstage when the focus mapping has ended;

FIG. 41 is a flow chart for explaining an embodiment of the devicemanufacturing method; and

FIG. 42 is a flow chart which shows a concrete example of step 204 ofFIG. 41.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described,referring to FIGS. 1 to 40.

FIG. 1 shows a schematic configuration of an exposure apparatus 100related to the embodiment.

Exposure apparatus 100 is a scanning exposure apparatus of thestep-and-scan method, namely the so-called scanner. As it will bedescribed later, a projection optical system PL is arranged in theembodiment, and in the description below, a direction parallel to anoptical axis AX of projection optical system PL will be described as theZ-axis direction, a direction within a plane orthogonal to the Z-axisdirection in which a reticle and a wafer are relatively scanned will bedescribed as the Y-axis direction, a direction orthogonal to the Z-axisand the Y-axis will be described as the X-axis direction, and rotational(inclination) directions around the X-axis, the Y-axis, and the Z-axiswill be described as θx, θy, and θz directions, respectively.

Exposure apparatus 100 includes an illumination system 10, a reticlestage RST that holds a reticle R that is illuminated by an illuminationlight for exposure (hereinafter, referred to as “illumination light” or“exposure light”) IL from illumination system 10, a projection unit PUthat includes projection optical system PL that projects illuminationlight IL emitted from reticle R on a wafer W, a stage unit 50 that has awafer stage WST and a measurement stage MST, their control system, andthe like. On wafer stage WST, wafer W is mounted.

Illumination system 10 is configured including a light source, anilluminance uniformity optical system, which includes an opticalintegrator and the like, and n illumination optical system that has areticle blind and the like (none of which are shown), as is disclosedin, for example, Kokai (Japanese Patent Unexamined ApplicationPublication) No. 2001-313250 (the corresponding U.S. Patent ApplicationPublication No. 2003/0025890 description) and the like. In illuminationsystem 10, a slit-shaped illumination area extending in the X-axisdirection which is set on reticle R with a reticle blind (a maskingsystem) is illuminated by illumination light (exposure light) IL with asubstantially uniform illuminance. In this case, as illumination lightIL, for example, an ArF excimer laser beam (wavelength 193 nm) is used.Further, as the optical integrator, for example, a fly-eye lens, a rodintegrator (an internal reflection type integrator), a diffractiveoptical element or the like can be used.

On reticle stage RST, reticle R on which a circuit pattern or the likeis formed on its pattern surface (the lower surface in FIG. 1) is fixed,for example, by vacuum chucking. Reticle stage RST is finely drivable ormovable in within an XY plane by a reticle stage drive section 11 (notshown in FIG. 1, refer to FIG. 6) that includes a linear motor or thelike, and reticle stage RST is also drivable in a predetermined scanningdirection (in this case, the Y-axis direction, which is the lateraldirection of the page surface in FIG. 1) at a designated scanning speed.

The positional information (including rotation information in the θzdirection) of reticle stage RST in the movement plane is constantlydetected, for example, at a resolution of around 0.5 to 1 nm by areticle laser interferometer (hereinafter referred to as a “reticleinterferometer”) 116, via a movable mirror 15 (the mirrors actuallyarranged are a Y movable mirror that has a reflection surface which isorthogonal to the Y-axis direction and an X movable mirror that has areflection surface orthogonal to the X-axis direction). The measurementvalues of reticle interferometer 116 are sent to a main controller 20(not shown in FIG. 1, refer to FIG. 6). Main controller 20 computes theposition of reticle stage RST in the X-axis direction, Y-axis direction,and the θz direction based on the measurement values of reticleinterferometer 116, and also controls the position (and velocity) ofreticle stage RST by controlling reticle stage drive section 11 based onthe computation results. Incidentally, instead of movable mirror 15, theedge surface of reticle stage RSV can be mirror polished so as to form areflection surface (corresponding to the reflection surface of movablemirror 15). Further, reticle interferometer 116 can measure positionalinformation of reticle stage RST related to at least one of the Z-axis,θx, or θy directions.

Projection unit PU is placed below reticle stage RST in FIG. 1.Projection unit PU includes a barrel 40, and projection optical systemPL that has a plurality of optical elements which are held in apredetermined positional relation inside barrel 40. As projectionoptical system PL, for example, a dioptric system is used, consisting ofa plurality of lenses (lens elements) that is disposed along an opticalaxis AX, which is parallel to the Z-axis direction. Projection opticalsystem PL is, for example, a both-side telecentric dioptric system thathas a predetermined projection magnification (such as one-quarter,one-fifth, or one-eighth times). Therefore, when illumination light ILfrom illumination system 10 illuminates illumination area IAR, a reducedimage of the circuit pattern (a reduced image of a part of the circuitpattern) of the reticle is formed within illumination area IAR, withillumination light IL that has passed through reticle R which is placedso that its pattern surface substantially coincides with a first plane(an object plane) of projection optical system PL, in an area conjugateto illumination area IAR on wafer W (exposure area) whose surface iscoated with a resist (a sensitive agent) and is placed on a second plane(an image plane) side, via projection optical system PL (projection unitPU) and liquid Lq (refer to FIG. 1). And by reticle stage RST and waferstage WST being synchronously driven, the reticle is relatively moved inthe scanning direction (the Y-axis direction) with respect toillumination area IAR (illumination light IL) while wafer W isrelatively moved in the scanning direction (the Y-axis direction) withrespect to the exposure area (illumination light IL), thus scanningexposure of a shot area (divided area) on wafer W is performed, and thepattern of the reticle is transferred onto the shot area. That is, inthe embodiment, the pattern is generated on wafer W according toillumination system 10, the reticle, and projection optical system PL,and then by the exposure of the sensitive layer (resist layer) on waferW with illumination light IL, the pattern is formed on wafer W. Althoughit is not shown in the drawings, projection unit PU is mounted on abarrel platform supported by three struts via a vibration isolationmechanism, however, as is disclosed in, for example, the pamphlet ofInternational Publication No. WO 2006/038952 and the like, projectionunit PU can be supported by suspension with respect to a mainframemember (not shown) placed above projection unit PU or with respect to abase member on which reticle stage RST is placed.

Further, in exposure apparatus 100 of the embodiment, in order toperform exposure applying the liquid immersion method, a nozzle unit 32that constitutes part of a local liquid immersion unit 8 is arranged soas to enclose the periphery of the lower end portion of barrel 40 thatholds an optical element that is closest to an image plane side (wafer Wside) that constitutes projection optical system FPL, which is a lens(hereinafter, also referred to a “tip lens”) 191 in this case. In theembodiment, as shown in FIG. 1, the lower end surface of nozzle unit 32is set to be substantially flush with the lower end surface of tip lens191. Further, nozzle unit 32 is equipped with a supply opening and arecovery opening of liquid Lq, a lower surface to which wafer W isplaced facing and at which the recovery opening is arranged, and asupply flow channel and a recovery flow channel that are connected to aliquid supply pipe 31A and a liquid recovery pipe 31B respectively. Asshown in FIG. 3, liquid supply pipe 31A and liquid recovery pipe 31B areinclined at an angle of 45 degrees with respect to the X-axis directionand the Y-axis direction in a planer view (when viewed from above) andare symmetrically placed with respect to a straight line LV in theY-axis direction that passes through optical axis AX of projectionoptical system PL.

One end of a supply pipe (not shown) is connected to liquid supply pipe31A while the other end of the supply pipe is connected to a liquidsupply unit 5 (not shown in FIG. 1, refer to FIG. 6), and one end of arecovery pipe (not shown) is connected to liquid recovery pipe 31B whilethe other end of the recovery pipe is connected to a liquid recoveryunit 6 (not shown in FIG. 1, refer to FIG. 6).

Liquid supply unit 5 includes a liquid tank, a compression pump, atemperature controller, a valve for controlling supply/stop of theliquid to liquid supply pipe 31A, and the like. As the valve, forexample, a flow rate control valve is preferably used so that not onlythe supply/stop of the liquid but also the adjustment of flow rate canbe performed. The temperature controller adjusts the temperature of theliquid within the liquid tank to nearly the same temperature, forexample, as the temperature within the chamber (not shown) where theexposure apparatus is housed. Incidentally, the tank for supplying theliquid, the compression pump, the temperature controller, the valve, andthe like do not all have to be equipped in exposure apparatus 100, andat least part of them can also be substituted by the equipment or thelike available in the plant where exposure apparatus 100 is installed.

Liquid recovery unit 6 includes a liquid tank, a suction pump, a valvefor controlling recovery/stop of the liquid via liquid recovery pipe31B, and the like. As the valve, a flow rate control valve is preferablyused corresponding to the valve of liquid supply unit 5. Incidentally,the tank for recovering the liquid, the suction pump, the valve, and thelike do not all have to be equipped in exposure apparatus 100, and atleast part of them can also be substituted by the equipment or the likeavailable in the plant where exposure apparatus 100 is installed.

In the embodiment, as the liquid described above, pure water(hereinafter, it will simply be referred to as “water” besides the casewhen specifying is necessary) that transmits the ArF excimer laser light(light with a wavelength of 193 nm) is to be used. Pure water can beobtained in large quantities at a semiconductor manufacturing plant orthe like without difficulty, and it also has an advantage of having noadverse effect on the photoresist on the wafer, to the optical lenses orthe like.

Refractive index n of the water with respect to the ArF excimer laserlight is around 1.44. In the water the wavelength of illumination lightIL is 193 nm×1/n, shorted to around 134 nm.

Liquid supply unit 5 and liquid recovery unit 6 each have a controller,and the respective controllers are controlled by main controller 20(refer to FIG. 6). According to instructions from main controller 20,the controller of liquid supply unit 5 opens the valve connected toliquid supply pipe 31A to a predetermined degree to supply water Lq(refer to FIG. 1) to the space between tip lens 191 and wafer W vialiquid supply pipe 31A, the supply flow channel and the supply opening.Further, when the water is supplied, according to instructions from maincontroller 20, the controller of liquid recovery unit 6 opens the valveconnected to liquid recovery pipe 31B to a predetermined degree torecover water Lq from the space between tip lens 191 and wafer W intoliquid recovery unit 6 (the liquid tank) via the recovery opening, therecovery flow channel and liquid recovery pipe 31B. During the supplyand recovery operations, main controller 20 gives commands to thecontrollers of liquid supply unit 5 and liquid recovery unit 6 so thatthe quantity of water supplied to the space between tip lens 191 andwafer W constantly equals the quantity of water recovered from thespace. Accordingly, a constant quantity of water Lq is held (refer toFIG. 1) in the space between tip lens 191 and wafer W. In this case,water Lq held in the space between tip lens 191 and wafer W isconstantly replaced.

As is obvious from the above description, in the embodiment, localliquid immersion unit 8 is configured including nozzle unit 32, liquidsupply unit 5, liquid recovery unit 6, liquid supply pipe 31A and liquidrecovery pipe 31B, and the like. Local liquid immersion unit 8 fillsliquid Lq in the space between tip lens 191 and wafer W by nozzle unit32, so that a local liquid immersion space (equivalent to a liquidimmersion area 14) which includes the optical path space of illuminationlight IL is formed. Accordingly, nozzle unit 32 is also called a liquidimmersion space formation member or a containment member (or, aconfinement member). Incidentally, part of local liquid immersion unit8, for example, at least nozzle unit 32 may also be supported in asuspended state by a main frame (including the barrel platform) thatholds projection unit PU, or may also be arranged at another framemember that is separate from the main frame. Or, in the case projectionunit PU is supported in a suspended state as is described earlier,nozzle unit 32 may also be supported in a suspended state integrallywith projection unit PU, but in the embodiment, nozzle unit 32 isarranged on a measurement frame that is supported in a suspended stateindependently from projection unit PU. In this case, projection unit PUdoes not have to be supported in a suspended state.

Incidentally, also in the case measurement stage MST is located belowprojection unit PU, the space between a measurement table (to bedescribed later) and tip lens 191 can be filled with water in a similarmanner to the manner described above.

Incidentally, in the description above, one liquid supply pipe (nozzle)and one liquid recovery pipe (nozzle) were arranged as an example,however, the present invention is not limited to this, and aconfiguration having multiple nozzles as is disclosed in, for example,the pamphlet of International Publication No. WO 99/49504, may also beemployed, in the case such an arrangement is possible taking intoconsideration a relation with adjacent members. Further, the lowersurface of nozzle unit 32 can be placed near the image plane (morespecifically, a wafer) of projection optical system PL rather than theoutgoing plane of tip lens 191, or, in addition to the optical path ofthe image plane side of tip lens 191, a configuration in which theoptical path on the object plane side of tip lens 191 is also filledwith liquid can be employed. The point is that any configuration can beemployed, as long as the liquid can be supplied in the space betweenoptical member (tip lens) 191 in the lowest end constituting projectionoptical system PL and wafer W. For example, the liquid immersionmechanism disclosed in the pamphlet of International Publication No. WO2004/053955, or the liquid immersion mechanism disclosed in the EPPatent Application Publication No. 1 420 298 can also be applied to theexposure apparatus of the embodiment.

Referring back to FIG. 1, stage unit 50 is equipped with wafer stage WSTand measurement stage MST that are placed above a base board 12, aninterferometer system 118 (refer to FIG. 6) including Y interferometers16 and 18 that measure position information of stages WST and MST, anencoder system (to be described later) that is used for measuringposition information of wafer stage WST on exposure or the like, a stagedrive system 124 (refer to FIG. 6) that drives stages WST and MST, andthe like.

On the bottom surface of each of wafer stage WST and measurement stageMST, a noncontact bearing (not shown), for example, a vacuum preloadtype hydrostatic air bearing (hereinafter, referred to as an “air pad”)is arranged at a plurality of points. Wafer stage WST and measurementstage MST are supported in a noncontact manner via a clearance of aroundseveral μm above base board 12, by static pressure of pressurized airthat is blown out from the air pad toward the upper surface of baseboard 12. Further, stages WST and MST are independently drivable intwo-dimensional directions, which are the Y-axis direction (a horizontaldirection of the page surface of FIG. 1) and the X-axis direction (anorthogonal direction to the page surface of FIG. 1) in a predeterminedplane (the XY plane), by stage drive system 124.

To be more specific, on a floor surface, as shown in the planar view inFIG. 2, a pair of Y-axis stators 86 and 87 extending in the Y-axisdirection are respectively placed on one side and the other side in theX-axis direction with base board 12 in between. Y-axis stators 86 and 87are each composed of, for example, a magnetic pole unit thatincorporates a permanent magnet group that is made up of a plurality ofsets of a north pole magnet and a south pole magnet that are placed at apredetermined distance and alternately along the Y-axis direction. AtY-axis stators 86 and 87, two Y-axis movers 82 and 84, and two Y-axismovers 83 and 85 are respectively arranged in a noncontact engagedstate. In other words, four Y-axis movers 82, 84, 83 and 85 in total arein a state of being inserted in the inner space of Y-axis stator 86 or87 whose XZ sectional surface has a U-like shape, and are severallysupported in a noncontact manner via a clearance of, for example, aroundseveral μm via the air pad (not shown) with respect to correspondingY-axis stator 86 or 87. Each of Y-axis movers 82, 84, 83 and 85 iscomposed of, for example, an armature unit that incorporates armaturecoils placed at a predetermined distance along the Y-axis direction.That is, in the embodiment, Y-axis movers 82 and 84 made up of thearmature units and Y-axis stator 86 made up of the magnetic pole unitconstitute moving coil type Y-axis linear motors respectively.Similarly, Y-axis movers 83 and 85 and Y-axis stator 87 constitutemoving coil type Y-axis linear motors respectively. In the followingdescription, each of the four Y-axis linear motors described above isreferred to as a Y-axis linear motor 82, a Y-axis linear motor 84, aY-axis linear motor 83 and a Y-axis linear motor 85 as needed, using thesame reference codes as their movers 82, 84, 83 and 85.

Movers 82 and 83 of two Y-axis linear motors 82 and 83 out of the fourY-axis linear motors are respectively fixed to one end and the other endin a longitudinal direction of an X-axis stator 80 that extends in theX-axis direction. Further, movers 84 and 85 of the remaining two Y-axislinear motors 84 and 85 are fixed to one end and the other end of anX-axis stator 81 that extends in the X-axis direction. Accordingly,X-axis stators 80 and 81 are driven along the Y-axis by a pair of Y-axislinear motors 82 and 83 and a pair of Y-axis linear motors 84 and 85respectively.

Each of X-axis stators 80 and 81 is composed of, for example, anarmature unit that incorporates armature coils placed at a predetermineddistance along the X-axis direction.

One X-axis stator, X-axis stator 81 is arranged in a state of beinginserted in an opening (not shown) formed at a stage main section 91(not shown in FIG. 2, refer to FIG. 1) that constitutes part of waferstage WST. Inside the opening of stage main section 91, for example, amagnetic pole unit, which has a permanent magnet group that is made upof a plurality of sets of a north pole magnet and a south pole magnetplaced at a predetermined distance and alternately along the X-axisdirection, is arranged. This magnetic pole unit and X-axis stator 81constitute a moving magnet type X-axis linear motor that drives stagemain section 91 in the X-axis direction. Similarly, the other X-axisstator, X-axis stator 80 is arranged in a state of being inserted in anopening formed at a stage main section 92 (not shown in FIG. 2, refer toFIG. 1) that constitutes part of measurement stage MST. Inside theopening of stage main section 92, a magnetic pole unit, which is similarto the magnetic pole unit on the wafer stage WST side (stage mainsection 91 side), is arranged. This magnetic pole unit and X-axis stator80 constitute a moving magnet type X-axis linear motor that drivesmeasurement stage MST in the X-axis direction.

In the embodiment, each of the linear motors described above thatconstitute stage drive system 124 is controlled by main controller 20shown in FIG. 6. Incidentally, each linear motor is not limited toeither one of the moving magnet type or the moving coil type, and thetypes can appropriately be selected as needed.

Incidentally, by making thrust forces severally generated by a pair ofY-axis linear motors 84 and 85 be slightly different, yawing (rotationquantity in the θz direction) of wafer stage WST can be controlled.Further, by making thrust forces severally generated by a pair of Y-axislinear motors 82 and 83 be slightly different, yawing of measurementstage MST can be controlled.

Wafer stage WST includes stage main section 91 previously described anda wafer table WTB that is mounted on stage main section 91. Wafer tableWTB and stage main section 91 are finely driven relative to base board12 and X-axis stator 81 in the Z-axis direction, the θx direction, andthe θy direction by a Z leveling mechanism (not shown) (including, forexample, a voice coil motor and the like). More specifically, wafertable WTB is finely movable in the Z-axis direction and can also beinclined (tilted) with respect to the XY plane (or the image plane ofprojection optical system PL). Incidentally, in FIG. 6, stage drivesystem 124 is shown including each linear motor, the Z levelingmechanism, and the drive system of measurement stage MST describedabove. Further, wafer table WTB can also be configured finely movable inat least one of the X-axis, the Y-axis, and the θz directions.

On wafer table WTB, a wafer holder (not shown) that holds wafer W byvacuum suction or the like is arranged. The wafer holder may also beformed integrally with wafer table WTB, but in the embodiment, the waferholder and wafer table WTB are separately configured, and the waferholder is fixed inside a recessed portion of wafer table WTB, forexample, by vacuum suction or the like. Further, on the upper surface ofwafer table WTB, a plate (liquid repellent plate) 28 is arranged, whichhas the surface (liquid repellent surface) substantially flush with thesurface of a wafer mounted on the wafer holder to which liquid repellentprocessing with respect to liquid Lq is performed, has a rectangularouter shape (contour), and has a circular opening that is formed in thecenter portion and is slightly larger than the wafer holder (a mountingarea of the wafer). Plate 28 is made of materials with a low coefficientof thermal expansion, such as glasses or ceramics (such as Zerodur (thebrand name) of Schott AG, Al₂O₃, or TiC), and on the surface of plate28, a liquid repellent film is formed by, for example, fluorine resinmaterials, fluorine series resin materials such aspolytetrafluoroethylene (Teflon (registered trademark)), acrylic resinmaterials, or silicon series resin materials. Further, as shown in aplaner view of wafer table WTB (wafer stage WST) in FIG. 4A, plate 28has a first liquid repellent area 28 a whose outer shape (contour) isrectangular enclosing a circular opening, and a second liquid repellentarea 28 b that has a rectangular frame (annular) shape placed around thefirst liquid repellent area 28 a. On the first liquid repellent area 28a, for example, at the time of an exposure operation, at least part of aliquid immersion area 14 that is protruded from the surface of the waferis formed, and on the second liquid repellent area 28 b, scales for anencoder system (to be described later) are formed. Incidentally, atleast part of the surface of plate 28 does not have to be flush with thesurface of the wafer, that is, may have a different height from that ofthe surface of the wafer. Further, plate 28 may be a single plate, butin the embodiment, plate 28 is configured by combining a plurality ofplates, for example, first and second liquid repellent plates thatcorrespond to the first liquid repellent area 28 a and the second liquidrepellent area 28 b respectively. In the embodiment, pure water is usedas liquid Lq as is described above, and therefore, hereinafter the firstliquid repellent area 28 a and the second liquid repellent area 28 b arealso referred to as a first water repellent plate 28 a and a secondwater repellent plate 28 b.

In this case, exposure light IL is irradiated to the first waterrepellent plate 28 a on the inner side, while exposure light IL ishardly irradiated to the second water repellent plate 28 b on the outerside. Taking this fact into consideration, in the embodiment, a firstwater repellent area to which water repellent coat having sufficientresistance to exposure light IL (light in a vacuum ultraviolet region,in this case) is applied is formed on the surface of the first waterrepellent plate 28 a, and a second water repellent area to which waterrepellent coat having resistance to exposure light IL inferior to thefirst water repellent area is applied is formed on the surface of thesecond water repellent plate 28 b. In general, since it is difficult toapply water repellent coat having sufficient resistance to exposurelight IL (light in a vacuum ultraviolet region, in this case) to a glassplate, it is effective to separate the water repellent plate into twosections in this manner, i.e. the first water repellent plate 28 a andthe second water repellent plate 28 b around it. Incidentally, thepresent invention is not limited to this, and two types of waterrepellent coat that have different resistance to exposure light IL mayalso be applied on the upper surface of the same plate in order to formthe first water repellent area and the second water repellent area.Further, the same kind of water repellent coat may be applied to thefirst and second water repellent areas. For example, only one waterrepellent area may also be formed on the same plate.

Further, as is obvious from FIG. 4A, at the end portion on the +Y sideof the first water repellent plate 28 a, a rectangular cutout is formedin the center portion in the X-axis direction, and a measurement plate30 is embedded inside the rectangular space (inside the cutout) that isenclosed by the cutout and the second water repellent plate 28 b. Afiducial mark FM is formed in the center in the longitudinal directionof measurement plate 30 (on a centerline LL of wafer table WTB), and apair of aerial image measurement slit patterns (slit-shaped measurementpatterns) SL are formed in the symmetrical placement with respect to thecenter of fiducial mark FM on one side and the other side in the X-axisdirection of fiducial mark FM. As each of aerial image measurement slitpatterns SL, an L-shaped slit pattern having sides along the Y-axisdirection and X-axis direction can be used, as an example.

Further, as shown in FIG. 4B, at the wafer stage WST section below eachof aerial image measurement slit patterns SL, an L-shaped housing 36 inwhich an optical system containing an objective lens, a mirror, a relaylens and the like is housed is attached in a partially embedded statepenetrating through part of the inside of wafer table WTB and stage mainsection 91. Housing 36 is arranged in pairs corresponding to the pair ofaerial image measurement slit patterns SL, although omitted in thedrawing.

The optical system inside housing 36 guides illumination light IL thathas been transmitted through aerial image measurement slit pattern SLalong an L-shaped route and emits the light toward a −Y direction.Incidentally, in the following description, the optical system insidehousing 36 is described as a light-transmitting system 36 by using thesame reference code as housing 36 for the sake of convenience.

Moreover, on the upper surface of the second water repellent plate 28 b,multiple grid lines are directly formed in a predetermine pitch alongeach of four sides. More specifically, in areas on one side and theother side in the X-axis direction of the second water repellent plate28 b (both sides in the horizontal direction in FIG. 4A), Y scales 39Y₁and 39Y₂ are formed, respectively. Y scales 39Y₁ and 39Y₂ are eachcomposed of a reflective grating (e.g. diffraction grating) having aperiodic direction in the Y-axis direction in which grid lines 38 havingthe longitudinal direction in the X-axis direction are formed in apredetermined pitch along a direction parallel to the Y-axis (Y-axisdirection).

Similarly, in areas on one side and the other side in the Y-axisdirection of the second water repellent plate 28 b (both sides in thevertical direction in FIG. 4A), X scales 39X₁ and 39X₂ are formedrespectively. X scales 39X₁ and 39X₂ are each composed of a reflectivegrating (e.g. diffraction grating) having a periodic direction in theX-axis direction in which grid lines 37 having the longitudinaldirection in the Y-axis direction are formed in a predetermined pitchalong a direction parallel to the X-axis (X-axis direction).

As each of the scales, the scale made up of a reflective diffractiongrating RG (refer to FIG. 7) that is created by, for example, hologramor the like on the surface of the second water repellent plate 28 b isused. In this case, each scale has gratings made up of narrow slits,grooves or the like that are marked at a predetermined distance (pitch)as graduations. The type of diffraction grating used for each scale isnot limited, and not only the diffraction grating made up of grooves orthe like that are mechanically formed, but also, for example, thediffraction grating that is created by exposing interference fringe on aphotosensitive resin may be used. However, each scale is created bymarking the graduations of the diffraction grating, for example, in apitch between 138 nm to 4 μm, for example, a pitch of 1 μm on a thinplate shaped glass. These scales are covered with the liquid repellentfilm (water repellent film) described above. Incidentally, the pitch ofthe grating is shown much wider in FIG. 4A than the actual pitch, forthe sake of convenience. The same is true also in other drawings.

In this manner, in the embodiment, since the second water repellentplate 28 b itself constitutes the scales, a glass plate with low-thermalexpansion is to be used as the second water repellent plate 28 b.However, the present invention is not limited to this, and a scalemember made up of a glass plate or the like with low-thermal expansionon which a grating is formed may also be fixed on the upper surface ofwafer table WTB, by a plate spring (or vacuum suction) or the like so asto prevent local shrinkage/expansion. In this case, a water repellentplate to which the same water repellent coat is applied on the entiresurface may be used instead of plate 28. Or, wafer table WTB may also beformed by a low thermal expansion material, and in such a case, a pairof Y scales and a pair of X scales may be directly formed on the uppersurface of wafer table WTB.

Incidentally, in order to protect the diffraction grating, it is alsoeffective to cover the grating with a glass plate with low thermalexpansion that has liquid repellency. In this case, the thickness of theglass plate, for example, is 1 mm, and the glass plate is set on theupper surface of the wafer table WST so that its surface is at the sameheight same as the wafer surface. Accordingly, the distance between thesurface of wafer W held on wafer stage WST and the grating surface ofthe scale in the Z-axis direction is 1 mm.

Incidentally, a lay out pattern is arranged for deciding the relativeposition between an encoder head and a scale near the edge of the scale(to be described later). The lay out pattern is configured from gridlines that have different reflectivity, and when the encoder head scansthe pattern, the intensity of the output signal of the encoder changes.Therefore, a threshold value is determined beforehand, and the positionwhere the intensity of the output signal exceeds the threshold value isdetected. Then, the relative position between the encoder head and thescale is set, with the detected position as a reference.

In the embodiment, main controller 20 can obtain the displacement ofwafer stage WST in directions of six degrees of freedom (the Z, X, Y,θz, θx, and θy directions) in the entire stroke area from themeasurement results of interferometer system 118 (refer to FIG. 6). Inthis case, interferometer system 118 includes X interferometers 126 to128, Y interferometer 16, and Z interferometers 43A and 43B.

To the −Y edge surface and the −X edge surface of wafer table WTB,mirror-polishing is applied, respectively, and a reflection surface 17 aand a reflection surface 17 b shown in FIG. 2 are formed. By severallyprojecting an interferometer beam (measurement beam) to reflectionsurface 17 a and reflection surface 17 b and receiving a reflected lightof each beam, Y interferometer 16 and X interferometers 126, 127, and128 (X interferometers 126 to 128 are not shown in FIG. 1, refer to FIG.2) of interferometer system 118 (refer to FIG. 6) measure a displacementof each reflection surface from a datum position (generally, a fixedmirror is placed on the side surface of projection unit PU, and thesurface is used as a reference surface), that is, positional informationof wafer stage WST within the XY plane, and the measurement values aresupplied to main controller 20. In the embodiment, as it will bedescribed later on, as each interferometer a multiaxial interferometerthat has a plurality of measurement axes is used with an exception for apart of the interferometers.

Meanwhile, to the side surface on the −Y side of stage main section 91,a movable mirror 41 having the longitudinal direction in the X-axisdirection is attached via a kinematic support mechanism (not shown), asshown in FIGS. 1 and 4B.

A pair of Z interferometers 43A and 43B (refer to FIGS. 1 and 2) thatconfigures a part of interferometer system 118 (refer to FIG. 6) andirradiates measurement beams on movable mirror 41 is arranged facingmovable mirror 41. To be more specific, as it can be seen when viewingFIGS. 2 and 4B together, movable mirror 41 is designed so that thelength in the X-axis direction is longer than reflection surface 17 a ofwafer table WTB by at least the interval of Z interferometers 43A and43B. Further, movable mirror 41 is composed of a member having ahexagonal cross-section shape as in a rectangle and an isoscelestrapezoid that has been integrated. Mirror-polishing is applied to thesurface on the −Y side of movable mirror 41, and three reflectionsurfaces 41 b, 41 a, and 41 c are formed.

Reflection surface 41 a configures the edge surface on the −Y side ofmovable mirror 41, and reflection surface 41 a is parallel with the XZplane and also extends in the X-axis direction. Reflection surface 41 bconfigures a surface adjacent to the +Z side of reflection surface 41 a,and reflection surface 41 b is parallel with a plane inclined in aclockwise direction in FIG. 4B at a predetermined angle with respect tothe XZ plane and also extends in the X-axis direction. Reflectionsurface 41 c configures a surface adjacent to the −Z side of reflectionsurface 41 a, and is arranged symmetrically with reflection surface 41b, with reflection surface 41 b in between.

As it can be seen when viewing FIGS. 1 and 2 together, Z interferometers43A and 43B are placed apart on one side and the other side of Yinterferometer 16 in the X-axis direction at a substantially equaldistance and at positions slightly lower than Y interferometer 16,respectively.

From each of the Z interferometers 43A and 43B, as shown in FIG. 1,measurement beam B1 along the Y-axis direction is projected towardreflection surface 41 b, and measurement beam B2 along the Y-axisdirection is projected toward reflection surface 41 c (refer to FIG.4B). In the embodiment, fixed mirror 47A having a reflection surfaceorthogonal to measurement beam B1 reflected off reflection surface 41 band a fixed mirror 47B having a reflection surface orthogonal tomeasurement beam B2 reflected off reflection surface 41 c are arranged,each extending in the X-axis direction at a position distanced apartfrom movable mirror 41 in the −Y-direction by a predetermined distancein a state where the fixed mirrors do not interfere with measurementbeams B1 and B2.

Fixed mirrors 47A and 47B are supported, for example, by the samesupport body (not shown) arranged in the frame (not shown) whichsupports projection unit PU. Incidentally, fixed mirrors 47A and 47B canbe arranged in the measurement frame or the like previously described.Further, in the embodiment, movable mirror 41 having three reflectionsurfaces 41 b, 41 a, and 41 c and fixed mirrors 47A and 47B werearranged, however, the present invention is not limited to this, and forexample, a configuration in which a movable mirror having an inclinedsurface of 45 degrees is arranged on the side surface of stage mainsection 91 and a fixed mirror is placed above wafer stage WST can beemployed. In this case, the fixed mirror can be arranged in the supportbody previously described or in the measurement frame.

Y interferometer 16, as shown in FIG. 2, projects measurement beams B4₁and B4₂ on reflection surface 17 a of wafer table WTB along ameasurement axis in the Y-axis direction spaced apart by an equaldistance to the −X side and the +X side from a straight line that isparallel to the Y-axis which passes through the projection center(optical axis AX, refer to FIG. 1) of projection optical system PL, andby receiving each reflected light, detects the position of wafer tableWTB in the Y-axis direction (a Y position) at the irradiation point ofmeasurement beams B4₁ and B4₂. Incidentally, in FIG. 1, measurementbeams B4₁ and B4₂ are representatively shown as measurement beam B4.

Further, Y interferometer 16 projects a measurement beam B3 towardreflection surface 41 a along a measurement axis in the Y-axis directionwith a predetermined distance in the Z-axis direction spaced betweenmeasurement beams B4₁ and B4₂, and by receiving measurement beam B3reflected off reflection surface 41 a, detects the Y position ofreflection surface 41 a (more specifically wafer stage WST) of movablemirror 41.

Main controller 20 computes the Y position (or to be more precise,displacement ΔY in the Y-axis direction) of reflection surface 17 a, ormore specifically, wafer table WTB (wafer stage WST), based on anaverage value of the measurement values of the measurement axescorresponding to measurement beams B4₁ and B4₂ of Y interferometer 16.Further, main controller 20 computes displacement (yawing amount)Δθz^((Y)) in the θz direction of wafer stage WST, based on a differenceof the measurement values of the measurement axes corresponding tomeasurement beams B4₁ and B4₂. Further, main controller 20 computesdisplacement (pitching amount) Δθx in the θx direction of wafer stageWST, based on the Y position (displacement ΔY in the Y-axis direction)of reflection surface 17 a and reflection surface 41 a.

Further, as shown in FIG. 2, X interferometer 126 projects measurementbeams B5₁ and B5₂ on wafer table WTB along the dual measurement axesspaced apart from straight line LH previously described by the samedistance, and based on the measurement values of the measurement axescorresponding to measurement beams B5₁ and B5₂, main controller 20computes a position (an X position, or to be more precise, displacementΔX in the X-axis direction) of wafer stage WST in the X-axis direction.Further, main controller 20 computes displacement (yawing amount)Δθz^((X)) of wafer stage WST in the θz direction from a difference ofthe measurement values of the measurement axes corresponding tomeasurement beams B5₁ and B5₂. Incidentally, Δθz^((X)) obtained from Xinterferometer 126 and Δθz^((Y)) obtained from Y interferometer 16 areequal to each other, and represents displacement (yawing amount) Δθz ofwafer stage WST in the θz direction.

Further, as is indicated in a dotted line in FIG. 2, a measurement beamB7 is emitted from X interferometer 128 along a measurement axisparallel to the X-axis. X interferometer 128 actually projectsmeasurement beam B7 on reflection surface 17 b of wafer table WTBlocated in the vicinity of an unloading position UP and a loadingposition LP along a measurement axis, which is parallel to the X-axisand joins unloading position UP and loading position LP (refer to FIG.3) as in the description later on. Further, as shown in FIG. 2, ameasurement beam B6 from X interferometer 127 is projected on reflectionsurface 17 b of wafer table WTB. Measurement beam B6 is actuallyprojected on reflection surface 17 b of wafer table WTB along ameasurement axis parallel to the X-axis that passes through thedetection center of a primary alignment system AL1.

Main controller 20 can obtain displacement ΔX of wafer table WTB in theX-axis direction from the measurement values of length measurement beamB6 of X interferometer 127 and the measurement values of lengthmeasurement beam B7 of X interferometer 128. However, the three Xinterferometers 126, 127, and 128 are placed differently regarding theY-axis direction, and X interferometer 126 is used at the time ofexposure as shown in FIG. 27, X interferometer 127 is used at the timeof wafer alignment as shown in FIG. 34 and the like, and Xinterferometer 128 is used at the time of wafer loading shown in FIG. 32and wafer unloading shown in FIG. 30.

Further from Z interferometers 43A and 43B, measurement beams B1 and B2that proceed along the Y-axis are projected toward movable mirror 41,respectively. These measurement beams B1 and B2 are incident onreflection surfaces 41 b and 41 c of movable mirror 41, respectively, ata predetermined angle of incidence (the angle is to be θ/2). Then,measurement beams B1 and B2 are reflected off reflection surfaces 41 band 41 c, respectively, and are incident on the reflection surfaces offixed mirrors 47A and 47B perpendicularly. And then, measurement beamsB1 and B2, which were reflected off the reflection surface of fixedmirrors 47A and 47B, are reflected off reflection surfaces 41 b and 41 cagain (returns the optical path at the time of incidence), respectively,and are received by Z interferometers 43A and 43B.

In this case, when displacement of wafer stage WST (more specificallymovable mirror 41) in the Y-axis direction is ΔYo and displacement inthe Z-axis direction is ΔZo, an optical path length change ΔL1 ofmeasurement beam B1 and an optical path length change ΔL2 of measurementbeam B2 received at of Z interferometers 43A and 43B can respectively beexpressed as in formulas (1) and (2) below.

ΔL1=ΔYo*(1+cos θ)−ΔZo*sin θ  (1)

ΔL2=ΔYo*(1+cos θ)+ΔZo*sin θ  (2)

Accordingly, from formulas (1) and (2), ΔZo and ΔYo can be obtainedusing the following formulas (3) and (4).

ΔZo=(ΔL2−ΔL1)/2 sin θ  (3)

ΔYo=(ΔL1+ΔL2)/{2(1+cos θ)}  (4)

Displacements ΔZo and ΔYo above can be obtained with Z interferometers43A and 43B. Therefore, displacement which is obtained using Zinterferometer 43A is to be ΔZoR and ΔYoR, and displacement which isobtained using Z interferometer 43B is to be ΔZoL and ΔYoL. And thedistance between measurement beams B1 and B2 projected by Zinterferometers 43A and 43B, respectively, in the X-axis direction is tobe a distance D (refer to FIG. 2). Under such premises, displacement(yawing amount) Δθz of movable mirror 41 (more specifically wafer stageWST) in the θz direction and displacement (rolling amount) Δθy ofmovable mirror 41 (more specifically wafer stage WST) in the θydirection can be obtained by the following formulas (5) and (6).

Δθz≅(ΔYoR−ΔYoL)/D  (5)

Δθy≅(ΔZoL−ΔZoR)/D  (6)

Accordingly, by using the formulas (3) to (6) above, main controller 20can compute displacement of wafer stage WST in four degree of freedom,ΔZo, ΔYo, Δθz, and Δθy, based on the measurement results of Zinterferometers 43A and 43B.

In the manner described above, from the measurement results ofinterferometer system 118, main controller 20 can obtain displacement ofwafer stage WST in directions of six degrees of freedom (Z, X, Y, θz,θx, and θy directions). Incidentally, in the embodiment, interferometersystem 118 could measure the positional information of wafer stage WSTin directions of six degrees of freedom, however, the measurementdirection is not limited to directions of six degrees of freedom, andthe measurement direction can be directions of five degrees of freedomor less.

Incidentally, as the main error cause of an interferometer, there is aneffect of air fluctuation which occurs by a temperature change and atemperature gradient of the atmosphere on a beam optical path. When awavelength λ of light changes from λ to λ+Δλ by air fluctuation, becausethe change of a phase difference KΔL due to a minute change Δλ of thiswavelength is wave number K=2π/λ, 2τΔL Δλ/λ² can be obtained. In thiscase, when wavelength of light λ=1 μm and minute change Δλ=1 nm, thephase change becomes 2π*100 with respect to an optical path differenceΔL=100 mm. This phase change corresponds to displacement which is 100times the measurement unit. In the case the optical path length which isset is long as is described, the interferometer is greatly affected bythe air fluctuation which occurs in a short time, and is inferior inshort-term stability. In such a case, it is desirable to use an encoder.

Incidentally, in the embodiment, the case has been described where waferstage WST (91, WTB) is a single stage that can move in six degrees offreedom, however, the present invention is not limited to this, andwafer stage WST can be configured including stage main section 91 whichcan move freely in the XY plane, and wafer table WTB mounted on stagemain section 91 that can be finely driven relative to stage main section91 at least in the Z-axis direction, the θx direction, and the θydirection. In this case, movable mirror 41 described earlier is arrangedin wafer table WTB. Further, instead of reflection surface 17 a andreflection surface 17 b, a movable mirror consisting of a plane mirrorcan be arranged in wafer table WTB.

However, in the embodiment, positional information (positionalinformation in directions of three degrees of freedom including rotaryinformation in the θz direction) of wafer stage WST (wafer table WTB) inthe XY plane is mainly measured by an encoder system described later on,and the measurement values of interferometer 16, 126, and 127 are usedsecondarily as backup or the like, such as in the case of correcting(calibrating) a long-term change (due to, for example, temporaldeformation of a scale) of the measurement values of the encoder system,and in the case of output abnormality in the encoder system.Incidentally, in the embodiment, of the positional information of waferstage WST in directions of six degrees of freedom, positionalinformation in directions of three degrees of freedom including theX-axis direction, the Y-axis direction and the θz direction is measuredby the encoder system described later on, and the remaining directionsof three degrees of freedom, or more specifically, the positionalinformation in the Z-axis direction, the θx direction, and the θydirection is measured by a measurement system which will also bedescribed later that has a plurality of Z sensors. Positionalinformation of the remaining directions of three degrees of freedom canbe measured by both the measurement system and interferometer system118. For example, positional information in the Z-axis direction and theθy direction can be measured by the measurement system, and positionalinformation in the θx direction can be measured by interferometer system118.

Incidentally, at least part of interferometer system 118 (such as anoptical system) may be arranged at the main frame that holds projectionunit PU, or may also be arranged integrally with projection unit PU thatis supported in a suspended state as is described above, however, in theembodiment, interferometer system 118 is to be arranged at themeasurement frame described above.

Measurement stage MST includes stage main section 92 previouslydescribed, and measurement table MTB mounted on stage main section 92.Measurement table MTB is mounted on stage main section 92, via the Zleveling mechanism (not shown). However, the present invention is notlimited to this, and for example, measurement stage MST can employ theso-called coarse and fine movement structure in which measurement tableMTB can be finely driven in the X-axis direction, the Y-axis direction,and the θz direction with respect to stage main section 92, ormeasurement table MTB can be fixed to stage main section 92, and all ofmeasurement stage MST including measurement table MTB and stage mainsection 92 can be configured drivable in directions of six degrees offreedom.

Various measurement members are arranged at measurement table MTB (andstage main section 92). As such measurement members, for example, asshown in FIGS. 2 and 5A, members such as an uneven illuminance measuringsensor 94 that has a pinhole-shaped light-receiving section whichreceives illumination light IL on an image plane of projection opticalsystem PL, an aerial image measuring instrument 96 that measures anaerial image (projected image) of a pattern projected by projectionoptical system PL, a wavefront aberration measuring instrument 98 by theShack-Hartman method that is disclosed in, for example, the pamphlet ofInternational Publication No. WO 03/065428 and the like are employed.

As wavefront aberration measuring instrument 98, the one disclosed in,for example, the pamphlet of International Publication No. WO 99/60361(the corresponding EP Patent Application Publication No. 1 079 223) canalso be used. As irregular illuminance sensor 94, the configurationsimilar to the one that is disclosed in, for example, Kokai (JapaneseUnexamined Patent Application Publication) No. 57-117238 (thecorresponding U.S. Pat. No. 4,465,368) and the like can be used.Further, as aerial image measuring instrument 96, the configurationsimilar to the one that is disclosed in, for example, Kokai (JapaneseUnexamined Patent Application Publication) No. 2002-014005 (thecorresponding U.S. Patent Application Publication No. 2002/0041377) andthe like can be used. Incidentally, three measurement members (94, 96and 98) are to be arranged at measurement stage MST in the embodiment,however, the types and/or the number of measurement members are/is notlimited to them. As the measurement members, for example, measurementmembers such as a transmittance measuring instrument that measures atransmittance of projection optical system PL, and/or a measuringinstrument that observes local liquid immersion unit 8, for example,nozzle unit 32 (or tip lens 191) or the like may also be used.Furthermore, members different from the measurement members such as acleaning member that cleans nozzle unit 32, tip lens 191 or the like mayalso be mounted on measurement stage MST.

In the embodiment, as it can be seen from FIG. 5A, the sensors that arefrequently used such as irregular illuminance sensor 94 and aerial imagemeasuring instrument 96 are placed on a centerline CL (Y-axis passingthrough the center) of measurement stage MST. Therefore, in theembodiment, measurement using these sensors can be performed by movingmeasurement stage MST only in the Y-axis direction without moving themeasurement stage in the X-axis direction.

In addition to each of the sensors described above, an illuminancemonitor that has a light-receiving section having a predetermined areasize that receives illumination light IL on the image plane ofprojection optical system PL may also be employed, which is disclosedin, for example, Kokai (Japanese Unexamined Patent ApplicationPublication) No. 11-016816 (the corresponding U.S. Patent ApplicationPublication No. 2002/0061469) and the like. The illuminance monitor isalso preferably placed on the centerline.

Incidentally, in the embodiment, liquid immersion exposure is performedin which wafer W is exposed with exposure light (illumination light) ILvia projection optical system PL and liquid (water) Lq, and accordinglyirregular illuminance sensor 94 (and the illuminance monitor), aerialimage measuring instrument 96 and wavefront aberration measuringinstrument 98 that are used in measurement using illumination light ILreceive illumination light IL via projection optical system PL andwater. Further, only part of each sensor such as the optical system maybe mounted on measurement table MTB (and stage main section 92), or theentire sensor may be placed on measurement table MTB (and stage mainsection 92).

As shown in FIG. 5B, a frame-shaped attachment member 42 is fixed to theend surface on the −Y side of stage main section 92 of measurement stageMST. Further, to the end surface on the −Y side of stage main section92, a pair of photodetection systems 44 are fixed in the vicinity of thecenter position in the X-axis direction inside an opening of attachmentmember 42, in the placement capable of facing a pair oflight-transmitting systems 36 described previously. Each ofphotodetection systems 44 is composed of an optical system such as arelay lens, a light receiving element such as a photomultiplier tube,and a housing that houses them.

As it can be easily imagined from FIGS. 4B and 5B and the description sofar, in the embodiment, in a state where wafer stage WST and measurementstage MST are closer together within a predetermined distance in theY-axis direction (including a contact state), illumination light IL thathas been transmitted through each aerial image measurement slit patternSL of measurement plate 30 is guided by each light-transmitting system36 and received by the light-receiving element of each photodetectionsystem 44.

That is, measurement plate 30, light-transmitting systems 36 andphotodetection systems 44 constitute an aerial image measuring unit 45(refer to FIG. 6), which is similar to the one disclosed in Kokai(Japanese Unexamined Patent Application Publication) No. 2002-014005(the corresponding U.S. Patent Application Publication No. 2002/0041377)referred to previously, and the like.

On attachment member 42, a confidential bar (hereinafter, shortlyreferred to as a “CD bar”) 46 that is made up of a bar-shaped memberhaving a rectangular sectional shape and serves as a reference member isarranged extending in the X-axis direction.

CD bar 46 is kinematically supported on measurement stage MST by afull-kinematic mount structure. Since CD bar 46 serves as a prototypestandard (measurement standard), an optical glass ceramic that has a lowthermal expansion, such as Zerodur (the brand name) of Schott AG isemployed as the material. The flatness degree of the upper surface (thesurface) of CD bar 46 is set high to be around the same level as aso-called datum plane plate. Further, as shown in FIG. 5A, a referencegrating (e.g. diffraction grating) 52 whose periodic direction is theY-axis direction is respectively formed in the vicinity of the endportions on one side and the other side in the longitudinal direction ofCD bar 46. The pair of reference gratings 52 are formed placed apartfrom each other at a predetermined distance (which is to be “L”) in thesymmetrical placement with respect to the center in the X-axis directionof CD bar 46, that is, centerline CL described above. For example,distance L is distance more than 400 mm incidentally.

Further, on the upper surface of CD bar 46, a plurality of referencemarks M are formed in the placement as shown in FIG. 5A. The pluralityof reference marks M are formed in three-row arrays in the Y-axisdirection in the same pitch, and the array of each row is formed beingshifted from each other by a predetermined distance in the X-axisdirection. As each of reference marks M, a two-dimensional mark having asize that can be detected by a primary alignment system and secondaryalignment systems (to be described later) is used. Reference mark M mayalso be different in shape (constitution) from fiducial mark FM, but inthe embodiment, reference mark M and fiducial mark FM have the sameconstitution and also they have the same constitution with that of analignment mark of wafer W. Incidentally, in the embodiment, the surfaceof CD bar 46 and the surface of measurement table MTB (which may includethe measurement members described above) are also covered with a liquidrepellent film (water repellent film) severally.

Also on the +Y end surface and the −X end surface of measurement tableMTB, reflection surfaces 19 a and 19 b are formed similar to wafer tableWTB as is described above (refer to FIGS. 2 and 5A). By projecting aninterferometer beam (measurement beam), as shown in FIG. 2, onreflection surfaces 19 a and 19 b and receiving a reflected light ofeach interferometer beam, a Y interferometer 18 and an X interferometer130 (X-axis interferometer 130 is not shown in FIG. 1, refer to FIG. 2)of interferometer system 118 (refer to FIG. 6) measure a displacement ofeach reflection surface from a datum position, that is, positionalinformation of measurement stage MST (e.g. including at least positionalinformation in the X-axis and Y-axis directions and rotation informationin the θz direction), and the measurement values are supplied to maincontroller 20.

In exposure apparatus 100 of the embodiment, in actual, a primaryalignment system AL1 is placed on straight line LV passing through thecenter of projection unit PU (optical axis AX of projection opticalsystem PL, which also coincides with the center of exposure area IA inthe embodiment) and being parallel to the Y-axis, and has a detectioncenter at a position that is spaced apart from the optical axis at apredetermined distance on the −Y side as shown in FIG. 3, althoughomitted in FIG. 1 from the viewpoint of avoiding intricacy of thedrawing. Primary alignment system AL1 is fixed to the lower surface of amain frame (not shown) via a support member 54. On one side and theother side in the X-axis direction with primary alignment system AL1 inbetween, secondary alignment systems AL2₁ and AL2₂, and AL2₃ and AL2₄whose detection centers are substantially symmetrically placed withrespect to straight line LV are severally arranged. That is, fivealignment systems AL1 and AL2₁ to AL2₄ are placed so that theirdetection centers are placed at different positions in the X-axisdirection, that is, placed along the X-axis direction.

As is representatively shown by secondary alignment system AL2₄, eachsecondary alignment system AL2_(n) (n=1 to 4) is fixed to a tip (turningend) of an arm 56 _(n) (n=1 to 4) that can turn around a rotation centerO as the center in a predetermined angle range in clockwise andanticlockwise directions in FIG. 3. In the embodiment, a part of eachsecondary alignment system AL2_(n) (e.g. including at least an opticalsystem that irradiates an alignment light to a detection area and alsoleads the light that is generated from a subject mark within thedetection area to a light-receiving element) is fixed to arm 56 _(n) andthe remaining section is arranged at the main frame that holdsprojection unit PU. The X-positions of secondary alignment systems AL2₁,AL2₂, AL2₃ and AL2₄ are severally adjusted by rotating around rotationcenter O as the center. In other words, the detection areas (or thedetection centers) of secondary alignment systems AL2₁, AL2₂, AL2₃ andAL2₄ are independently movable in the X-axis direction. Accordingly, therelative positions of the detection areas of primary alignment systemAL1 and secondary alignment systems AL2₁, AL2₂, AL2₃ and AL2₄ areadjustable in the X-axis direction. Incidentally, in the embodiment, theX-positions of secondary alignment systems AL2₁, AL2₂, AL2₃ and AL2₄ areto be adjusted by the rotation of the arms. However, the presentinvention is not limited to this, and a drive mechanism that drivessecondary alignment systems AL2₁, AL2₂, AL2₃ and AL2₄ back and forth inthe X-axis direction may also be arranged. Further, at least one ofsecondary alignment systems AL2₁, AL2₂, AL2₃ and AL2₄ can be moved notonly in the X-axis direction but also in the Y-axis direction.Incidentally, since part of each secondary alignment system AL2_(n) ismoved by arm 56 _(n), positional information of the part that is fixedto arm 56 _(n) is measurable by a sensor (not shown) such as, forexample, an interferometer or an encoder. The sensor may only measureposition information in the X-axis direction of secondary alignmentsystem AL2_(n), or may be capable of measuring position information inanother direction, for example, the Y-axis direction and/or the rotationdirection (including at least one of the θx and θy directions).

On the upper surface of each arm 56 _(n), a vacuum pad 58 _(n) (n=1 to4) that is composed of a differential evacuation type air bearing isarranged. Further, arm 56 _(n) is rotated by a rotation drive mechanism60 _(n) (n=1 to 4, not shown in FIG. 3, refer to FIG. 6) that includes amotor or the like, in response to instructions of main controller 20.Main controller 20 activates each vacuum pad 58 _(n) to fix each arm 56_(n) to a main frame (not shown) by suction after rotation adjustment ofarm 56 _(n). Thus, the state of each arm 56 _(n) after rotation angleadjustment, that is, a desired positional relation of four secondaryalignment systems AL2₁ to AL2₄ with respect to primary alignment systemAL1 is maintained.

Incidentally, in the case a portion of the main frame facing arm 56 _(n)is a magnetic body, an electromagnet may also be employed instead ofvacuum pad 58.

In the embodiment, as each of primary alignment system AL1 and foursecondary alignment systems AL2₁ to AL2₄, for example, an FIA (FieldImage Alignment) system by an image processing method is used thatirradiates a broadband detection beam that does not expose resist on awafer to a subject mark, and picks up an image of the subject markformed on a light-receiving plane by the reflected light from thesubject mark and an image of an index (an index pattern on an indexplate arranged within each alignment system) (not shown), using animaging device (such as CCD), and then outputs their imaging signals.The imaging signal from each of primary alignment system AL1 and foursecondary alignment systems AL2₁ to AL2₄ is supplied to main controller20 in FIG. 6.

Incidentally, each of the alignment systems described above is notlimited to the FIA system, and an alignment sensor, which irradiates acoherent detection light to a subject mark and detects a scattered lightor a diffracted light generated from the subject mark or makes twodiffracted lights (e.g. diffracted lights of the same order ordiffracted lights being diffracted in the same direction) generated fromthe subject mark interfere and detects an interference light, cannaturally be used alone or in combination as needed. Further, fivealignment systems AL1 and AL2₁ to AL2₄ are to be arranged in theembodiment. However, the number of alignment systems is not limited tofive, but may be the number equal to or more than two and equal to orless than four, or may be the number equal to or more than six, or maybe the even number, not the odd number. Moreover, in the embodiment,five alignment systems AL1 and AL2₁ to AL2₄ are to be fixed to the lowersurface of the main frame that holds projection unit PU, via supportmember 54. However, the present invention is not limited to this, andfor example, the five alignment systems may also be arranged on themeasurement frame described earlier. Further, because alignment systemsAL1 and AL2₁ to AL2₄ detect alignment marks on wafer W and referencemarks on and CD bar 46, in the embodiment, the systems will also besimply referred to as a mark detection system.

In exposure apparatus 100 of the embodiment, as shown in FIG. 3, fourhead units 62A to 62D of the encoder system are placed in a state ofsurrounding nozzle unit 32 on all four sides. In actual, head units 62Ato 62D are fixed to the foregoing main frame that holds projection unitPU in a suspended state via a support member, although omitted in FIG. 3from the viewpoint of avoiding intricacy of the drawings. Incidentally,for example, in the case projection unit PU is supported in a suspendedstate, head units 62A to 62D may be supported in a suspended stateintegrally with projection unit PU, or may be arranged at themeasurement frame described above.

Head units 62A and 62C are respectively placed on the +X side and −Xside of projection unit PU having the longitudinal direction in theX-axis direction, and are also placed apart at the substantially samedistance from optical axis AX of projection optical system PLsymmetrically with respect to optical axis AX of projection opticalsystem PL. Further, head units 62B and 62D are respectively placed onthe +Y side and −Y side of projection unit PU having the longitudinaldirection in the Y-axis direction and are also placed apart at thesubstantially same distance from optical axis AX of projection opticalsystem PL.

As shown in FIG. 3, head units 62A and 62C are each equipped with aplurality of (six in this case) Y heads 64 that are placed at apredetermined distance on a straight line LH that passes through opticalaxis AX of projection optical system PL and is parallel to the X-axis,along the X-axis direction. Head unit 62A constitutes a multiple-lens(six-lens in this case) Y linear encoder (hereinafter, shortly referredto as a “Y encoder” or an “encoder” as needed) 70A (refer to FIG. 6)that measures the position in the Y-axis direction (the Y-position) ofwafer stage WST (wafer table WTB) using Y scale 39Y₁ described above.Similarly, head unit 62C constitutes a multiple-lens (six-lens, in thiscase) Y linear encoder 70C (refer to FIG. 6) that measures theY-position of wafer stage WST (wafer table WTB) using Y scale 39Y₂described above. In this case, a distance between adjacent Y heads 64(i.e. measurement beams) equipped in head units 62A and 62C is setshorter than a width in the X-axis direction of Y scales 39Y₁ and 39Y₂(to be more accurate, a length of grid line 38). Further, out of aplurality of Y heads 64 that are equipped in each of head units 62A and62C, Y head 64 located innermost is fixed to the lower end portion ofbarrel 40 of projection optical system PL (to be more accurate, to theside of nozzle unit 32 enclosing tip lens 191) so as to be placed asclose as possible to the optical axis of projection optical system PL.

As shown in FIG. 3, head unit 62B is equipped with a plurality of (sevenin this case) X heads 66 that are placed on straight line LV at apredetermined distance along the Y-axis direction. Further, head unit62D is equipped with a plurality of (eleven in this case, out of elevenX heads, however, three X heads that overlap primary alignment systemAL1 are not shown in FIG. 3) X heads 66 that are placed on straight lineLV at a predetermined distance. Head unit 62B constitutes amultiple-lens (seven-lens, in this case) X linear encoder (hereinafter,shortly referred to as an “X encoder” or an “encoder” as needed) 70B(refer to FIG. 6) that measures the position in the X-axis direction(the X-position) of wafer stage WST (wafer table WTB) using X scale 39X₁described above. Further, head unit 62D constitutes a multiple-lens(eleven-lens, in this case) X linear encoder 70D (refer to FIG. 6) thatmeasures the X-position of wafer stage WST (wafer table WTB) using Xscale 39X₂ described above. Further, in the embodiment, for example, atthe time of alignment (to be described later) or the like, two X heads66 out of eleven X heads 66 that are equipped in head unit 62Dsimultaneously face X scale 39X₁ and X scale 39X₂ respectively in somecases. In these cases, X scale 39X₁ and X head 66 facing X scale 39X₁constitute X linear encoder 70B, and X scale 39X₂ and X head 66 facing Xscale 39X₂ constitute X linear encoder 70D.

Herein, some of eleven X heads 66, in this case, three X heads areattached to the lower surface side of support member 54 of primaryalignment system AL1. Further, a distance between adjacent X heads 66(measurement beams) that are equipped in each of head units 62B and 62Dis set shorter than a width in the Y-axis direction of X scales 39X₁ and39X₂ (to be more accurate, a length of grid line 37). Further, X head 66located innermost out of a plurality of X heads 66 that are quipped ineach of head units 62B and 62D is fixed to the lower end portion of thebarrel of projection optical system PL (to be more accurate, to the sideof nozzle unit 32 enclosing tip lens 191) so as to be placed as close aspossible to the optical axis of projection optical system PL.

Moreover, on the −X side of secondary alignment system AL2₁ and on the+X side of secondary alignment system AL2₄, Y heads 64 y ₁ and 64 y ₂are respectively arranged, whose detection points are placed on astraight line parallel to the X-axis that passes through the detectioncenter of primary alignment system AL1 and are substantiallysymmetrically placed with respect to the detection center. The distancebetween Y heads 64 y ₁ and 64 y ₂ is set substantially equal to distanceL described previously. Y heads 64 y ₁ and 64 y ₂ face Y scales 39Y₂ and39Y₁ respectively in a state where the center of wafer W on wafer stageWST is on straight line LV as shown in FIG. 3. On an alignment operation(to be described later) or the like, Y scales 39Y₂ and 39Y₁ are placedfacing Y heads 64 y ₁ and 64 y ₂ respectively, and the Y-position (andthe θz rotation) of wafer stage WST is measured by Y heads 64 y ₁ and 64y ₂ (i.e. Y encoders 70C and 70A composed of Y heads 64 y ₁ and 64 y ₂).

Further, in the embodiment, at the time of baseline measurement of thesecondary alignment systems (to be described later) or the like, a pairof reference gratings 52 of CD bar 46 face Y heads 64 y ₁ and 64 y ₂respectively, and the Y-position of CD bar 46 is measured at theposition of each of reference gratings 52 by Y heads 64 y ₁ and 64 y ₂and facing reference gratings 52. In the following description, encodersthat are composed of Y heads 64 y ₁ and 64 y ₂ facing reference gratings52 respectively are referred to as Y-axis linear encoders 70E and 70F(refer to FIG. 6).

Six linear encoders 70A to 70F described above measure the positionalinformation of wafer stage WST in each measurement direction at aresolution of, for example, around 0.1 nm, and the measurement values(measurement information) are supplied to main controller 20. Maincontroller 20 controls the position within the XY plane of wafer tableWTB based on the measurement values of linear encoders 70A to 70D, andalso controls the rotation in the θz direction of CD bar 46 based on themeasurement values of linear encoders 70E and 70F. Incidentally, theconfiguration and the like of the linear encoder will be describedfurther later in the description.

In exposure apparatus 100 of the embodiment, a position measuring unitthat measures positional information of wafer W in the Z-axis directionis arranged. As shown in FIG. 3, in the embodiment, as the positionmeasuring unit, a multipoint focal position detecting system(hereinafter, shortly referred to as a “multipoint AF system”) by anoblique incident method is arranged, which is composed of an irradiationsystem 90 a and a photodetection system 90 b, and has the configurationsimilar to the one disclosed in, for example, Kokai (Japanese UnexaminedPatent Application Publication) No. 06-283403 (the corresponding U.S.Pat. No. 5,448,332) and the like. In the embodiment, as an example,irradiation system 90 a is placed on the −Y side of the −X end portionof head unit 62C and photodetection system 90 b is placed on the −Y sideof the +X end portion of head unit 62A in a state of opposingirradiation system 90 a.

A plurality of detection points of the multipoint AF system (90 a, 90 b)are placed at a predetermined distance along the X-axis direction on thesurface to be detected, although it is omitted in the drawings. In theembodiment, the plurality of detection points are placed, for example,in the arrangement of a matrix having one row and M columns (M is atotal number of detection points) or having two rows and N columns (N isa half of a total number of detection points). In FIG. 3, the pluralityof detection points to which a detection beam is severally irradiatedare not individually shown, but are shown as an elongate detection area(beam area) AF that extends in the X-axis direction between irradiationsystem 90 a and photodetection system 90 b. Since the length ofdetection area AF in the X-axis direction is set to around the same asthe diameter of wafer W, position information (surface positioninformation) in the Z-axis direction across the entire surface of waferW can be measured by only scanning wafer W in the Y-axis direction once.Further, since detection area AF is placed between liquid immersion area14 (exposure area IA) and the detection areas of the alignment systems(AL1, AL2₁, AL2₂, AL2₃ and AL2₄) in the Y-axis direction, the detectionoperations of the multipoint AF system and the alignment systems can beperformed in parallel. The multipoint AF system may also be arranged onthe main frame that holds projection unit PU or the like, but is to bearranged on the measurement frame described earlier in the embodiment.

Incidentally, the plurality of detection points are to be placed in onerow and M columns, or two rows and N columns, but the number(s) of rowsand/or columns is/are not limited to these numbers. However, in the casethe number of rows is two or more, the positions in the X-axis directionof detection points are preferably made to be different even between thedifferent rows. Moreover, the plurality of detection points is to beplaced along the X-axis direction. However, the present invention is notlimited to this, and all of or some of the plurality of detection pointsmay also be placed at different positions in the Y-axis direction. Forexample, the plurality of detection points may also be placed along adirection that intersects both of the X-axis and the Y-axis. That is,the positions of the plurality of detection points only have to bedifferent at least in the X-axis direction. Further, a detection beam isto be irradiated to the plurality of detection points in the embodiment,but a detection beam may also be irradiated to, for example, the entirearea of detection area AF. Furthermore, the length of detection area AFin the X-axis direction does not have to be nearly the same as thediameter of wafer W.

In the embodiment, in the vicinity of detection points located at bothends out of a plurality of detection points of the multipoint AF system,that is, in the vicinity of both end portions of beam area AF, one eachpair of surface position sensors for Z position measurement(hereinafter, shortly referred to as “Z sensors”), that is, a pair of Zsensors 72 a and 72 b and a pair of Z sensors 72 c and 72 d are arrangedin the symmetrical placement with respect to straight line LV. Z sensors72 a to 72 d are fixed to the lower surface of a main frame (not shown).As Z sensors 72 a to 72 d, a sensor that irradiates a light to wafertable WTB from above, receives the reflected light and measures positioninformation of the wafer table WTB surface in the Z-axis directionorthogonal to the XY plane, as an example, an optical displacementsensor (sensor by an optical pickup method), which has the configurationlike an optical pickup used in a CD drive unit, is used. Incidentally, Zsensors 72 a to 72 d may also be arranged on the measurement framedescribed above or the like.

Moreover, head unit 62C is equipped with a plurality of (in this casesix each, which is a total of twelve) Z sensors 74 _(i,j) (i=1, 2, j=1,2, . . . , 6), which are placed corresponding to each other along twostraight lines at a predetermined distance, the straight lines beingparallel to straight line LH and are located on one side and the otherside of straight line LH in the X-axis direction that connects aplurality of Y heads 64. In this case, Z sensors 74 _(1,j) and 74 _(2,j)that make a pair are disposed symmetrical to straight line LH.Furthermore, the plurality of pairs (in this case, six pairs) of Zsensors 74 _(1,j) and 74 _(2,j) and a plurality of Y heads 64 are placedalternately in the X-axis direction.

As each Z sensor 74 _(i,j), a sensor by an optical pickup method similarto Z sensors 72 a to 72 d is used.

In this case, the distance between each pair of Z sensors 74 _(1,j) and74 _(2,j) that are located symmetrically with respect to straight lineLH is set to be the same distance as the distance between Z sensors 74 aand 74 b previously described. Further, a pair of Z sensors 74 _(1,4)and 74 _(2,4) are located on the same straight line in the Y-axisdirection as Z sensors 72 a and 72 b.

Further, head unit 62A is equipped with a plurality of (twelve in thiscase) Z sensors 76 _(p,q) (p=1, 2 and q=1, 2, . . . , 6) that are placedsymmetrically to a plurality of Z sensors 74 _(i,j) with respect tostraight line LV. As each Z sensor 76 _(p,q), a sensor by an opticalpickup method similar to Z sensors 72 a to 72 d is used. Further, a pairof Z sensors 76 _(1,3) and 76 _(2,3) are located on the same straightline in the Y-axis direction as Z sensors 72 c and 72 d. Incidentally, Zsensors 74 _(i,j) and 76 _(p,q) are installed, for example, at themainframe or the measurement frame previously described. Further, in theembodiment, the measurement system that has Z sensors 72 a to 72 d, and74 _(i,j) and 76 _(p,q) measures positional information of wafer stageWST in the Z-axis direction using one or a plurality of Z sensors thatface the scale previously described. Therefore, in the exposureoperation, Z sensors 74 _(i,j) and 76 _(p,q) used for positionmeasurement are switched, according to the movement of wafer stage WST.Furthermore, in the exposure operation, Y scale 39Y₁ and at least one Zsensor 76 _(p,q) face each other, and Y scale 39Y₂ and at least one Zsensor 74 _(i,j) also face each other. Accordingly, the measurementsystem can measure not only positional information of wafer stage WST inthe Z-axis direction, but also positional information (rolling) in theθy direction. Further, in the embodiment, each Z sensor of themeasurement system detects a grating surface (a formation surface of adiffraction grating) of the scale, however, the measurement system canalso detect a surface that is different from the grating surface, suchas, for example, a surface of the cover glass that covers the gratingsurface.

Incidentally, in FIG. 3, measurement stage MST is omitted and a liquidimmersion area that is formed by water Lq held in the space betweenmeasurement stage MST and tip lens 191 is shown by a reference code 14.Further, in FIG. 3, a reference code 78 indicates a localair-conditioning system that blows dry air whose temperature is adjustedto a predetermined temperature to the vicinity of a beam path of themultipoint AF system (90 a, 90 b) by, for example, downflow as isindicated by outline arrows in FIG. 3. Further, a reference code UPindicates an unloading position where a wafer on wafer table WTB isunloaded, and a reference code LP indicates a loading position where awafer is loaded on wafer table WTB. In the embodiment, unloadingposition UP and loading position LP are set symmetrically with respectto straight line LV. Incidentally, unloading position UP and loadingposition LP may be the same position.

FIG. 6 shows the main configuration of the control system of exposureapparatus 100. The control system is mainly configured of maincontroller 20 composed of a microcomputer (or workstation) that performsoverall control of the entire apparatus. In a memory 34 which is anauxiliary memory connecting to main controller 20, correctioninformation, which will be described below, is stored. Incidentally, inFIG. 6, various sensors such as irregular illuminance sensor 94, aerialimage measuring instrument 96 and wavefront aberration measuringinstrument 98 that are arranged at measurement stage MST arecollectively shown as a sensor group 99.

In the embodiment, by using encoder systems 70A to 70F (refer to FIG.6), main controller 20 can measure a position coordinate of wafer stageWST in directions of three degree of freedom (X, Y, θz), in an effectivestroke range of wafer stage WST, namely in an area where wafer stage WSTmoves for alignment and exposure operation.

The configuration of encoders 70A to 70F will be described now, focusingon Y encoder 70A that is enlargedly shown in FIG. 7A, as arepresentative. FIG. 7A shows one Y head 64 of head unit 62A thatirradiates a detection light (measurement beam) to Y scale 39Y₁.

Y head 64 is mainly composed of three sections, which are an irradiationsystem 64 a, an optical system 64 b and a photodetection system 64 c.

Irradiation system 64 a includes a light source that emits a laser beamLB in a direction inclined at an angle of 45 degrees with respect to theY-axis and Z-axis, for example, a semiconductor laser LD, and aconverging lens L1 that is placed on the optical path of laser beam LBemitted from semiconductor laser LD.

Optical system 64 b is equipped with a polarization beam splitter PBSwhose separation plane is parallel to an XZ plane, a pair of reflectionmirrors R1a and R1b, lenses L2a and L2b, quarter wavelength plates(hereinafter, referred to as a λ/4 plate) WP1a and WP1b, refectionmirrors R2a and R2b, and the like.

Photodetection system 64 c includes a polarizer (analyzer), aphotodetector, and the like.

In Y encoder 70A, laser beam LB emitted from semiconductor laser LD isincident on polarization beam splitter PBS via lens L1, and is split bypolarization into two beams LB₁ and LB₂. Beam LB₁ having beentransmitted through polarization beam splitter PBS reaches reflectivediffraction grating RG that is formed on Y scale 39Y₁, via reflectionmirror R1a, and beam LB₂ reflected off polarization beam splitter PBSreaches reflective diffraction grating RG via reflection mirror R1b.Incidentally, “split by polarization” in this case means the splittingof an incident beam into a P-polarization component and anS-polarization component.

Predetermined-order diffraction beams that are generated fromdiffraction grating RG due to irradiation of beams LB₁ and LB₂, forexample, the first-order diffraction beams are severally converted intoa circular polarized light by λ/4 plates WP1b and WP1a via lenses L2band L2a, and reflected by reflection mirrors R2b and R2a and then thebeams pass through λ/4 plates WP1b and WP1a again and reach polarizationbeam splitter PBS by tracing the same optical path in the reverseddirection.

Each of the polarization directions of the two beams that have reachedpolarization beam splitter PBS is rotated at an angle of 90 degrees withrespect to the original direction. Therefore, the first-orderdiffraction beam of beam LB₁ that was previously transmitted throughpolarization beam splitter PBS is reflected off polarization beamsplitter PBS and is incident on photodetection system 64 c, and also thefirst-order diffraction beam of beam LB₂ that was previously reflectedoff polarization beam splitter PBS is transmitted through polarizationbeam splitter PBS and is synthesized concentrically with the first-orderdiffraction beam of beam LB₁ and is incident on photodetection system 64c.

Then, the polarization directions of the two first-order diffractionbeams described above are uniformly arranged by the analyzer insidephotodetection system 64 c and the beams interfere with each other to bean interference light, and the interference light is detected by thephotodetector and is converted into an electric signal in accordancewith the intensity of the interference light.

Then, when Y scale 39Y₁ (more specifically, wafer stage WST) moves in ameasurement direction (in this case, the Y-axis direction), the phase ofthe two beams changes, respectively, which changes the intensity of theinterference light. This change in the intensity of the interferencelight is detected by photodetection system 64 c, and positionalinformation corresponding to the intensity change is output as ameasurement value of Y encoder 70A. Other encoders 70B, 70C, 70D, 70E,and 70F are also configured similarly with encoder 70A.

As is obvious from the above description, in encoders 70A to 70F, sincethe optical path lengths of the two beams to be interfered are extremelyshort and also are almost equal to each other, the influence by airfluctuations can mostly be ignored. Incidentally, as each encoder, anencoder having a resolution of, for example, around 0.1 nm is used.

Incidentally, in the encoders of the embodiment, as shown in FIG. 7B,laser beam LB having a sectional shape that is elongated in the periodicdirection of grating RG may also be used, as a detection light. In FIG.7B, beam LB is overdrawn largely compared to grating RG.

Incidentally, as another form of the encoder head, there is a type inwhich only optical system 64 b is included in the encoder head andirradiation system 64 a and photodetection system 64 c are physicallyseparate from optical system 64 b. In this type of encoder, the threesections are optically connected via an optical fiber.

Next, a measurement principle of an encoder will be explained in detail,with Y encoder 70A shown in FIG. 7A serving as an example. First of all,a relation between the intensity of interference light that issynthesized from two return beams LB₁ and LB₂ and displacement (relativedisplacement with Y head 64) of Y scale 39Y₂ is derived.

When the two beams (beam) LB₁ and LB₂ are scattered by reflectiongrating RG that moves, the beams are subject to a frequency shift by aDoppler effect, or in other words, undergo a Doppler shift. FIG. 8Ashows a scatter of light by the moving reflection surface DS. However,vectors k₀ and k₁ in the drawing are to be parallel with a YZ plane, andreflection surface DS is to be parallel to the Y-axis and perpendicularto the Z-axis.

Supposing that reflection surface DS moves at a velocity vector v=vy+vz,or more specifically, moves in the +Y direction at a speed Vy (=|vy|)and also in the +Z direction at a speed Vz (=|vz|). To this reflectionsurface, the light of wave number vector k₀ is incident at an angle θ₀,and the light of wave number vector k₁ is scattered at an angle θ₁.However, |k₀|=|k₁|=k. The Doppler shift (frequency difference ofscattered light k₁ and incident light k₀) f_(D) that incident light k₀undergoes is given in the next formula (7).

$\begin{matrix}\begin{matrix}{{2\pi \; f_{D}} = {\left( {k_{1} - k_{0}} \right)*v}} \\{= {{2\; {KVy}\; {\cos \left\lbrack {\left( {\theta_{1} - \theta_{0}} \right)/2} \right\rbrack}\cos \; \theta} +}} \\{{2\; {KVz}\; {\cos \left\lbrack {\left( {\theta_{1} - \theta_{0}} \right)/2} \right\rbrack}\sin \; \theta}}\end{matrix} & (7)\end{matrix}$

In this case, since θ=π/2−(θ₁+θ₀)/2, the above formula is transformed soas to obtain the following formula (8).

2πf _(D) =KVy(sin θ₁+sin θ₀)+KVz(cos θ₁+cos θ₀)  (8)

Reflection surface DS is displaced during time Δt by displacement vectorvΔt, or more specifically, displaced in the +Y direction by a distanceΔY−VyΔt and in the +Z direction by a distance ΔZ−VzΔt. And with thisdisplacement, the phase of scattered light k₁ shifts by φ=2πf_(D)Δt.When substituting formula (8), phase shift φ can be obtained from thefollowing formula (9).

φ=KΔY(sin θ₁+sin θ₀)+KΔz(cos θ₁+cos θ₁)  (9)

In this case, a relation (a diffraction condition) expressed as in thefollowing formula is valid between incident angle θ₀ and scatteringangle θ₁.

sin θ₁+sin θ₀ =nλ/p  (10)

However, λ is the wavelength of the light, p is the pitch of thediffraction grating, and n is the order of diffraction. Incidentally,order of diffraction n becomes positive to a diffraction light scattered(generated) in the +Y direction, and becomes negative to a diffractionlight generated in the −Y-direction, with a zero order diffraction lightof scattering angle (diffraction angle) −θ₀ serving as a reference. Whenformula (10) is substituted into formula (9), phase shift φ can berewritten as in formula (11) below.

φ=2πnΔY/p+KΔZ(cos θ₁+cos θ₀)  (11)

As is obvious from formula (11) above, if reflection surface DS stops,or more specifically, ΔY=ΔZ=0, phase shift φ also becomes zero.

Using formula (11), phase shift of the two beams LB₁ and LB₂ areobtained. First of all, phase shift of beam LB₁ will be considered. InFIG. 8B, supposing that beam LB₁, which was reflected off reflectionmirror R1a, is incident on reflection grating RG at an angle θ_(a0), anda n_(a) ^(th) order diffraction light is to be generated at an angleθ_(a1). When the diffraction light is generated, the phase shift thatthe diffraction light undergoes becomes the same form as the right-handside of formula (11). And the return beam, which is reflected offreflection mirror R2a and follows the return path, is incident onreflection grating RG at an angle θ_(a1). Then, a diffraction light isgenerated again. In this case, the diffraction light that occurs atangle θ_(a0) and moves toward reflection mirror R1a following theoriginal optical path is an n_(a) ^(th) order diffraction light, whichis a diffraction light of the same order as the diffraction lightgenerated on the outward path. Accordingly, the phase shift which beamLB₁ undergoes on the return path is equal to the phase shift which beamLB₁ undergoes on the outward path. Accordingly, the total phase shiftwhich beam LB₁ undergoes is obtained as in the following formula (12).

φ₁=4πn _(a) ΔY/p+2KΔZ(cos θ_(a1)+cos θ_(a0))  (12)

However, a diffraction condition was given as in the next formula (13).

sin θ_(a1)+sin θ_(a0) =n _(a) λ/p  (13)

Meanwhile, beam LB₂ is incident on reflection grating RG at an angleθ_(b0), and an n_(b) ^(th) order diffraction light is generated at anangle θ_(b1). Supposing that this diffraction light is reflected offreflection mirror R2b and returns to reflection mirror R1b following thesame optical path. The total phase shift which beam LB₂ undergoes can beobtained as in the next formula (14), similar to formula (12).

φ₂=4πn _(b) ΔY/p+2KΔZ(cos θ_(b1)+cos θ_(b0))  (14)

However, a diffraction condition was given as in the next formula (15).

sin θ_(b1)+sin θ_(b0) =n _(b) λ/p  (15)

Intensity I of the interference light synthesized by the two returnbeams LB₁ and LB₂ is dependent on a phase difference φ between the tworeturn beams LB₁ and LB₂ in the light receiving position of thephotodetector, by I∝1+cos φ. However, the intensity of the two beams LB₁and LB₂ was to be equal to each other. In this case, phase difference φcan be obtained as a sum of a difference (more specifically φ₂−φ₁) ofphase shifts due to Y and Z displacements of each reflection grating RGof the two beams LB₁ and LB₂ and a phase difference (KΔL) due to opticalpath difference ΔL of the two beams LB₁ and LB₂, using a formula (12)and formula (14) as in the following formula (16).

φ=KΔL+4π(n _(b) −n _(a))ΔY/p+2KΔZf(θ_(a0),θ_(a1),θ_(b0),θ_(b1))+φ₀  (16)

In this case, a geometric factor, which is to be decided from theplacement of reflection mirrors R1a, R1b, R2a, and R2b and diffractionconditions (13) and (15), was expressed as in the following formula(17).

f(θ_(a0),θ_(a1),θ_(b0),θ_(b1))=cos θ_(b1)+cos θ_(b0)−cos θ_(a1)−cosθ_(a0)  (17)

Further, in formula (16) above, a constant phase term, which is to bedecided by other factors (e.g., a definition of the reference positionof displacements ΔL, ΔY, and ΔZ), was expressed as φ₀.

In this case, the encoder is to be configured so as to satisfy opticalpath difference ΔL=0 and a symmetry shown in the following formula (18).

θ_(a0)=θ_(b0),θ_(a1)=θ_(b1)  (18)

In such a case, inside the parenthesis of the third term on theright-hand side of formula (16) becomes zero, and also at the same timen_(b)=−n_(a) (=n), therefore, the following formula (19) can beobtained.

φ_(sym)(ΔY)=2πΔY/(p/4n)+φ₀  (19)

From formula (19) above, it can be seen that phase difference φ_(sym) isnot dependent on wavelength λ of the light. And, it can be seen thatintensity I of the interference light repeats strong and weakintensities each time displacement ΔY is increased or decreased by ameasurement unit (also referred to as a measurement pitch) of p/4n.Therefore, the number of times is measured of the strong and weakintensities of the interference light that accompanies displacement ΔYfrom a predetermined reference position. And by using a counting value(count value) c_(ΔY), a measurement value c_(ΔY) of displacement ΔY iscomputed from formula (20) below.

C _(ΔY)=(p/4n)*c _(ΔY)  (20)

Furthermore, by splitting a sinusoidal intensity change of theinterference light using interpolation instrument (an interpolator), itsphase φ′ (=φ_(sym)%2π) can be measured. In this case, measurement valueC_(ΔY) of displacement ΔY is computed according to the following formula(21).

C _(ΔY)=(p/4n)*[c _(ΔY)+(φ′−φ₀)/2π]  (21)

In formula (21) above, constant phase term φ₀ is to be a phase offset(however, 0≦φ₀<2π), and phase φ_(sym) (ΔY=0) at the reference positionof displacement ΔY is to be kept.

As it can be seen from the description so far above, by using aninterpolation instrument together, displacement A Y can be measured at ameasurement resolution whose measurement unit is (p/4n) or under. Themeasurement resolution in this case is decided from an interpolationerror or the like, due to a shift of an intensity changeI(ΔY)=I(φ_(sym)(ΔY)) of the interference light from an ideal sinusoidalwaveform according to displacement ΔY, which is a discretization error(also referred to as a quantization error) determined from a split unitof phase φ′. Incidentally, because the discretization unit ofdisplacement ΔY is, for example, one in several thousand of measurementunit (p/4n), which is sufficiently small about 0.1 nm, measurement valuec_(ΔY) of the encoder will be regarded as a continuous quantity unlessit is noted otherwise.

Meanwhile, when wafer stage WST moves in a direction different from theY-axis direction and a relative motion (a relative motion in a directionbesides the measurement direction) occurs between head 64 and Y scale39Y₁ in a direction besides the direction that should be measured, inmost cases, a measurement error occurs in Y encoder 70A due to suchmotion. In the description below, a mechanism of the generation of ameasurement error will be considered, based on the measurement principleof the encoder described above.

In this case, the change of phase difference φ indicated by formula (16)above in two cases shown in FIGS. 9A and 9B will be considered, as asimple example. First of all, in the case of FIG. 9A, an optical axis ofhead 64 coincides with the Z-axis direction (head 64 is not inclined).Supposing that wafer stage WST was displaced in the Z-axis direction(ΔZ≠0,ΔY=0). In this case, because there are no changes in optical pathdifference ΔL, there are no changes in the first term on the right-handside of formula (16). The second term becomes zero, according to asupposition ΔY=0. And, the third term becomes zero because it satisfiesthe symmetry of formula (18). Accordingly, no change occurs in phasedifference φ, and further no intensity change of the interference lightoccurs. As a consequence, the measurement values of the encoder also donot change.

Meanwhile, in the case of FIG. 9B, the optical axis of head 64 isinclined (head 64 is inclined) with respect to the Z-axis. Supposingthat wafer stage WST was displaced in the Z-axis direction from thisstate (ΔZ≠0,ΔY=0). In this case as well, because there are no changes inoptical path difference ΔL, there are no changes in the first term onthe right-hand side of formula (16). And, the second term becomes zero,according to supposition ΔY=0. However, because the head is inclined thesymmetry of formula (18) will be lost, and the third term will notbecome zero and will change in proportion to Z displacement ΔZ.Accordingly, a change occurs in phase difference φ, and as aconsequence, the measurement values change. Incidentally, even if head64 is not gradient, for example, the symmetry of formula (18) is lostdepending on the optical properties (such as telecentricity) of thehead, and count values change likewise. More specifically,characteristic information of the head unit, which is a generationfactor of the measurement error of the encoder system, includes not onlythe gradient of the head but also the optical properties as well.

Further, although it is omitted in the drawings, in the case wafer stageWST is displaced in a direction perpendicular to the measurementdirection (the Y-axis direction) and the optical axis direction (theZ-axis direction), (ΔX≠0,≠Y=0,ΔZ=0), the measurement values do notchange as long as the direction (longitudinal direction) in which thegrid line of diffraction grating RG faces is orthogonal to themeasurement direction, however, in the case the direction is notorthogonal, sensitivity occurs with a gain proportional to the angle.

Next, a case will be considered in which wafer stage WST rotates (theinclination changes), using FIGS. 10A to 10D. First of all, in the caseof FIG. 10A, the optical axis of head 64 coincides with the Z-axisdirection (head 64 is not inclined). Even if wafer stage WST isdisplaced in the +Z direction and moves to a condition shown in FIG. 10Bfrom this state, the measurement value of the encoder does not changesince the case is the same as in FIG. 9A previously described.

Next, suppose that wafer stage WST rotates around the X-axis from thestate shown in FIG. 10B and moves into a state shown in FIG. 10C. Inthis case, since the head and the scale do not perform relative motion,or more specifically, because a change occurs in optical path differenceΔL due to the rotation of wafer stage WST even though ΔY=ΔZ=0, themeasurement values of the encoder change. That is, a measurement erroroccurs in the encoder system due to an inclination (tilt) of wafer stageWST.

Next, suppose that wafer stage WST moves downward from a state shown inFIG. 10C and moves into a state shown in FIG. 10D. In this case, achange in optical path difference ΔL does not occur because wafer stageWST does not rotate. However, because the symmetry of formula (18) hasbeen lost, phase difference φ changes by Z displacement ΔZ through thethird term on the right-hand side of formula (16). Accordingly, themeasurement values of the encoder change. Incidentally, the count valueof the encoder in the case of FIG. 10D will be the same as the countvalue in the case of FIG. 10A.

According to a result of a simulation that the inventors and the likeperformed, it became clear that the measurement values of the encoderhave sensitivity not only to the displacement of the scale in the Y-axisdirection, which is the measurement direction but also have sensitivityto an attitude change in the θx direction (the pitching direction) andthe θz direction (the yawing direction), and moreover, depend on theposition change in the Z-axis direction in the case such as when thesymmetry has been lost as is previously described. That is, thetheoretical description previously described agreed with the result ofthe simulation.

Therefore, in the embodiment, correction information to correct themeasurement error of each encoder caused by the relative motion of thehead and the scale in the direction besides the measurement direction isacquired as follows.

a. First of all, main controller 20 drives wafer stage WST via stagedrive system 124, while monitoring the measurement values of Yinterferometer 16 of interferometer system 118, X interferometer 126,and Z interferometers 43A and 43B, and as shown in FIGS. 11A and 11B,makes Y head 64 located farthest to the −X side of head unit 62A face anarbitrary area (an area circled in FIG. 11A) AR of Y scale 39Y₁ on theupper surface of wafer table WTB.b. Then, based on the measurement values of Y interferometer 16 and Zinterferometers 43A and 43B, main controller 20 drives wafer table WTB(wafer stage WST) so that a rolling amount θy and yawing amount θz ofwafer table WTB (wafer stage WST) both become zero while a pitchingamount θx also becomes a desired value α₀ (in this case, α₀=200 μrad),irradiates a detection light on area AR of Y scale 39Y₁ from head 64above after the drive, and stores the measurement values whichcorrespond to a photoelectric conversion signal from head 64 which hasreceived the reflected light in an internal memory.c. Next, while maintaining the attitude (pitching amount θx=α₀, yawingamount θz=0, rolling amount θy=0) of wafer table WTB (wafer stage WST)based on the measurement values of Y interferometer 16 and Zinterferometers 43A and 43B, main controller 20 drives wafer table WTB(wafer stage WST) within a predetermined range, such as, for example,the range of −100 μm to +100 μm in the Z-axis direction as is indicatedby an arrow in FIG. 11B, sequentially takes in the measurement valuescorresponding to the photoelectric conversion signals from head 64 whichhas received the reflected light at a predetermined sampling intervalwhile irradiating a detection light on area AR of Y scale 39Y₁ from head64 during the drive, and stores the values in the internal memory.d. Next, main controller 20 changes pitching amount θx of wafer tableWTB (wafer stage WST) to (α=α₀−Δα), based on the measurement values of Yinterferometer 16.e. Then, as for the attitude after the change, main controller 20repeats an operation similar to c. described above.f. Then, main controller 20 alternately repeats the operations of d. ande described above, and for a range where pitching amount θx is, forexample, −200 μrad<θx<+200 μrad, takes in the measurement values of head64 within the Z drive range described above at Δα(rad), at an intervalof, for example, 40 μrad.g. Next, by plotting each data within the internal memory obtained bythe processes b. to e. described above on a two-dimensional coordinatesystem whose horizontal axis indicates a Z position and vertical axisindicates an encoder count value, sequentially linking plot points wherethe pitching amounts are the same, and shifting the horizontal axis inthe vertical axis direction so that a line (a horizontal line in thecenter) which indicates a zero pitching amount passes through theorigin, main controller 20 can obtain a graph (a graph that shows achange characteristic of the measurement values of the encoder (head)according to the Z leveling of the wafer stage) like the one shown inFIG. 12.

The values of the vertical axis at each point on the graph in FIG. 12 isnone other than the measurement error of the encoder in each Z position,in pitching amount θx=α. Therefore, main controller 20 sees pitchingamount θx, the Z position, and the encoder measurement error at eachpoint on the graph in FIG. 12 as a table data, and stores the table datain memory 34 (refer to FIG. 6) as stage position induced errorcorrection information. Or main controller 20 sees the measurement erroras a function of Z position z and pitching amount θx, and obtains thefunction computing an undetermined coefficient, for example, by theleast-squares method, and stores the function in memory 34 as stageposition induced error correction information.

h. Next, main controller 20 drives wafer stage WST in the −X-directionby a predetermined amount via stage drive system 124 while monitoringthe measurement values of X interferometer 126 of interferometer system118, and as shown in FIG. 13, makes Y head 64 located second from theedge on the −X side of head unit 62A (the Y head next to Y head 64 whosedata has already been acquired in the process described above) face areaAR previously described (the area circled in FIG. 13) of Y scale 39Y₁ onthe upper surface of wafer table WTB.i. Then, main controller 20 performs a process similar to the onesdescribed above on Y head 64, and stores correction information of Yencoder 70A configured by head 64 and Y scale 39Y₁ in memory 34.j. Hereinafter, in a similar manner, main controller 20 respectivelyobtains correction information of Y encoder 70A configured by eachremaining Y head 64 of head unit 62A and Y scale 39Y₁, correctioninformation of X encoder 70B configured by each X head 66 of head unit62B and X scale 39X₁, correction information of Y encoder 70C configuredby each X head 64 of head unit 62C and Y scale 39Y₂, and correctioninformation of X encoder 70D configured by each X head 66 of head unit62D and X scale 39X₂, and stores them in memory 34.

In this case, it is important that the same area on X scale 39X₁ is usedon the measurement using each X head 66 of head unit 62B describedabove, the same area on Y scale 39Y₂ is used on the measurement usingeach Y head 64 of head unit 62C, and the same area in X scale 39X₂ isused on the measurement using each Y head 66 of head unit 62D. Thereason for this is because if the correction (including the curvecorrection of reflection surfaces 17 a and 17 b, and reflection surfaces41 a, 41 b, and 41 c) of each interferometer of interferometer system118 has been completed, the attitude of wafer stage WST can be set to adesired attitude anytime based on the measurement values of theinterferometers, and by using the same location of each scale, even ifthe scale surface is inclined, the measurement error caused by theeffect of the inclination does not occur between the heads.

Further, main controller 20 performs the measurement described above forY heads 64 y ₁ and 64 y ₂ using the same area on Y scale 39Y₂ and 39Y₁,respectively, which is the same as each Y head 64 of head units 62C and64A described above, obtains correction information of encoder 70Cconfigured by Y head 64 y ₁ which faces Y scale 39Y₂ and correctioninformation of encoder 70A configured by Y head 64 y ₂ which faces Yscale 39Y₁, and stores the information in memory 34.

Next, in a similar procedure as in the case described above where thepitching amount was changed, main controller 20 sequentially changesyawing amount θz of wafer stage WST for a range of −200 μrad<θz<+200μrad and drives wafer table WTB (wafer stage WST) in the Z-axisdirection at each position within a predetermined range, such as, forexample, within −100 μm˜+100 μm, while maintaining both the pitchingamount and the rolling amount of wafer stage WST at zero, and during thedrive, sequentially takes in the measurement values of the head at apredetermined sampling interval and stores them in the internal memory.Such a measurement is performed for all heads 64 or 66, and in aprocedure similar to the one described earlier, by plotting each datawithin the internal memory on the two-dimensional coordinate systemwhose horizontal axis indicates the Z position and vertical axisindicates the encoder count value, sequentially linking plot pointswhere the yawing amounts are the same, and shifting the horizontal axisso that a line (a horizontal line in the center) which indicates a zeropitching amount passes through the origin, main controller 20 can obtaina graph similar to the one shown in FIG. 12. Then, main controller 20sees yawing amount θz, Z position z, and the encoder measurement errorat each point on the graph as a table data, and stores the table data inmemory 34 as correction information. Or, main controller 20 sees themeasurement error as a function of Z position z and yawing amount θz,and obtains the function computing an undetermined coefficient, forexample, by the least-squares method, and stores the function in memory34 as correction information.

In this case, the measurement error of each encoder in the case both thepitching amount and the yawing amount of wafer stage WST are not zerowhen wafer stage WST is at Z position z can safely be considered to be asimple sum of the measurement error that corresponds to the pitchingamount described above and the measurement error that corresponds to theyawing amount (a linear sum) when wafer stage WST is at Z position z.The reason for this is, as a result of simulation, it has been confirmedthat the measurement error (count value) linearly changes according tothe change of the Z position, even when the yawing is changed.

Hereinafter, to simplify the description, as for the Y heads of each Yencoder, a function of pitching amount θx, yawing amount θz, and Zposition z of wafer stage WST that expresses a measurement error Δy asshown in the next formula (22) is to be obtained, and to be stored inmemory 34. Further, as for the X heads of each X encoder, a function ofrolling amount θy, yawing amount θz, and Z position z of wafer stage WSTthat expresses a measurement error Δx as shown in the next formula (23)is to be obtained, and to be stored in memory 34.

Δy=f(z,θx,θz)=θx(z−a)+θz(z−b)  (22)

Δx=g(z,θy,θz)=θy(z−c)+θz(z−d)  (23)

In formula (22) above, a is a Z-coordinate of a point where eachstraight line intersects on the graph in FIG. 12, and b is aZ-coordinate of a point where each straight line intersects on a graphsimilar to FIG. 12 in the case when the yawing amount is changed so asto acquire the correction information of the Yencoder. Further, informula (23) above, c is a Z-coordinate of a point where each straightline intersects on a graph similar to FIG. 12 in the case when therolling amount is changed so as to acquire the correction information ofthe X encoder, and d is a Z-coordinate of a point where each straightline intersects on a graph similar to FIG. 12 in the case when theyawing amount is changed so as to acquire the correction information ofthe X encoder.

Incidentally, because Δy and Δx described above show the degree ofinfluence of the position of wafer stage WST in the direction besidesthe measurement direction (e.g. the θx direction, the θy direction, theθz direction and the Z-axis direction) on the measurement values of theY encoder or the X encoder, in the present specification, it will bereferred to as a stage position induced error, and because the stageposition induced error can be used as it is as correction information,the correction information will be referred to as stage position inducederror correction information.

Next, a calibration process of a head position for acquiring a positioncoordinate of each head in the XY plane, especially the positioncoordinate in the direction besides the measurement direction, whichbecomes a premise in processes such as a process to convert themeasurement value of an encoder to be described later into positionalinformation of wafer stage WST in the XY plane and a linkage processamong a plurality of encoders, will be described. In this case, as anexample, a calibration process of the position coordinate in thedirection besides the measurement direction (the X-axis direction)orthogonal to the measurement direction of Y head 64 configuring eachhead unit 62A and 62C will be described.

First of all, on starting this calibration process, main controller 20drives wafer stage WST so that Y scales 39Y₁ and 39Y₂ are located belowhead units 62A and 62C, respectively. For example, as shown in FIG. 14,Y head 64 _(A3), which is the third head from the left of head unit 62A,and Y head 64 _(C5), which is the second head from the right of headunit 62C, are made to face Y scales 39Y₁ and 39Y₂, respectively.

Next, based on the measurement values of measurement beams B4₁ and B4₂of Y interferometer 16, or the measurement values of Z interferometers43A and 43B, main controller 20 rotates wafer stage WST only by apredetermined angle (the angle being θ) within the XY plane with opticalaxis AX of projection optical system PL serving as a center as shown byan arrow RV in FIG. 14, and acquires the measurement values of encoders70A and 70C configured by Y heads 64 _(A3) and 64 _(C5) and Y scales39Y₁ and 39Y₂ facing Y heads 64 _(A3) and 64 _(C5), respectively, whichcan be obtained during the rotation. In FIG. 14, vectors MA and MB,which correspond to the measurement values measured during the rotationof wafer stage WST by Y heads 64 _(A3) and 64 _(C5), are respectivelyshown.

In this case, because θ is a very small angle, MA=b*θ and MB=a*θ arevalid, and a ratio MA/MB of the magnitude of vectors MA and MB are equalto a ratio a/b, which is a ratio of the distance from the rotationcenter to Y heads 64 _(A3) and 64 _(C5).

Therefore, main controller 20 computes distances b and a, or morespecifically, the X-coordinate values of Y heads 64 _(A3) and 64 _(C5),based on predetermined angle θ obtained from the measurement values ofencoders 70A and 70C and the measurement values of interferometer beamsB4₁ and B4₂, respectively, or, furthermore performs a calculation basedon the X-coordinate values that have been calculated, and computes thepositional shift amount (more specifically, correction information ofthe positional shift amount) of Y heads 64 _(A3) and 64 _(C5) in theX-axis direction with respect to the design position.

Further, in the case wafer stage WST is located at the position shown inFIG. 14, in actual practice, head units 62B and 62D face X scales 39X₁and 39X₂, respectively. Accordingly, on the rotation of wafer stage WSTdescribed above, main controller 20 simultaneously acquires themeasurement values of X scales 39X₁ and 39X₂ and encoders 70B and 70D,which are configured by one X head 66 each of head units 62B and 62Dthat respectively face X scale 39X₁ and 39X₂. Then, in a manner similarto the description above, main controller 20 computes the Y-coordinatevalues of one X head 66 each that respectively face X scale 39X₁ and39X₂, or, furthermore performs a calculation based on the computationresult, and computes the positional shift amount (more specifically,correction information of the positional shift amount) of the X heads inthe Y-axis direction with respect to the design position.

Next, main controller 20 moves wafer stage WST in the X-axis directionat a predetermined pitch, and by performing a processing similar to theprocedure described above at each positioning position, main controller20 can obtain the X-coordinate values, or the positional shift amount(more specifically, correction information of the positional shiftamount) in the X-axis direction with respect to the design position alsofor the remaining Y heads of head units 62A and 62C.

Further, by moving wafer stage WST in the Y-axis direction at apredetermined pitch from the position shown in FIG. 14 and performing aprocessing similar to the procedure described above at each positioningposition, main controller 20 can obtain the Y-coordinate values, or thepositional shift amount (more specifically, correction information ofthe positional shift amount) in the Y-axis direction with respect to thedesign position also for the remaining Y heads of head units 62B and62D.

Further, in a method similar to Y head 64 described above, maincontroller 20 acquires the X-coordinate values or the positional shiftamount (more specifically, correction information of the positionalshift amount) in the X-axis direction with respect to the designposition, also for Y heads 64 y ₁ and y₂.

In the manner described above, main controller 20 can acquire theX-coordinate values or the positional shift amount (more specifically,correction information of the positional shift amount) in the X-axisdirection with respect to the design position for all Y heads 64, 64 y₁, and 64 y ₂, and the Y-coordinate values or the positional shiftamount (more specifically, correction information of the positionalshift amount) in the Y-axis direction with respect to the designposition also for all X heads 66, therefore, the information that hasbeen acquired is stored in a storage unit, such as, for example, memory34. The X-coordinate values or the Y coordinate values or the positionalshift amount in the X-axis direction or the Y-axis direction withrespect to the design position of each head stored in memory 34, will beused such as when converting the measurement values of an encoder intopositional information within the XY plane of wafer stage WST, as itwill be described later on. Incidentally, on converting the measurementvalues of an encoder into positional information within the XY plane ofwafer stage WST or the like described later on, design values are usedfor the Y coordinate values of each Y head, and the X-coordinate valuesof each X head. This is because since the influence that the positioncoordinates of each head in the measurement direction has on the controlaccuracy of the position of wafer stage WST is extremely weak, (theeffectiveness to the control accuracy is extremely slow), it issufficient enough to use the design values.

Now, when there is an error (or a gap) between the height (the Zposition) of each scale surface (the grating surface) on wafer table WTBand the height of a reference surface including the exposure center (itis the center of exposure area IA previously described and coincideswith optical axis AX of projection optical system PL in the embodiment),the so-called Abbe error occurs in the measurement values of the encoderon rotation (pitching or rolling) around an axis (an X-axis or a Y-axis)parallel to the XY plane of wafer stage WST, therefore, this error needsto be corrected. In this case, the reference surface is a surface thatserves as a reference to displacement ΔZo of wafer stage WST in theZ-axis direction measured by interferometer system 118, and in theembodiment, the surface is to coincide with the image plane ofprojection optical system PL.

For the correction of the error described above, it is necessary toaccurately obtain the difference of height (the so-called Abbe offsetquantity) of each scale surface (the grating surface) with respect tothe reference surface of wafer stage WST. This is because correcting theAbbe errors due to the Abbe offset quantity described above is necessaryin order to accurately control the position of wafer stage WST withinthe XY plane using an encoder system. By taking into consideration suchpoints, in the embodiment, main controller 20 performs calibration forobtaining the Abbe offset quantity described above in the followingprocedure.

First of all, on starting this calibration processing, main controller20 drives wafer stage WST and moves Y scales 39Y₁ and 39Y₂ so that Yscales 39Y₁ and 39Y₂ are located under head units 62A and 62C,respectively. In this case, for example, as shown in FIG. 15, Y head 64_(A3) being the third head from the left of head unit 62A faces area ARwhich is a specific area on Y scale 39Y₁ where Y head 64 _(A3) had facedwhen acquiring the stage position induced error correction informationin the previous description. Further, in this case, as shown in FIG. 15,Y head 64 _(C4) being the fourth head from the left of head unit 62Cfaces an area which is a specific area on Y scale 39Y₂ where Y head 64_(C4) had faced when acquiring the stage position induced errorcorrection information in the previous description.

Next, based on measurement results of Y interferometer 16 which usesinterferometer beams B4₁, B4₂ and B3 previously described, maincontroller 20 tilts wafer stage WST around an axis that passes theexposure center and is parallel to the X-axis so that pitching amountΔθx becomes zero in the case displacement (pitching amount) Δθx of waferstage WST in the θx direction with respect to the XY plane is not zero,based on the measurement results of Y interferometer 16 ofinterferometer system 118. Because all the corrections of eachinterferometer of interferometer system 118 have been completed at thispoint, such pitching control of wafer stage WST becomes possible.

Then, after such adjustment of the pitching amount of wafer stage WST,main controller 20 acquires measurement values y_(A0) and y_(C0) ofencoders 70A and 70C, configured by Y scales 39Y₁ and 39Y₂ and Y heads64 _(A3) and 64 _(C4) that face Y scales 39Y₁ and 39Y₂, respectively.

Next, based on measurement results of Y interferometer 16, usinginterferometer beams B4₁, B4₂ and B3, main controller 20 tilts waferstage WST at an angle φ around the axis that passes the exposure centerand is parallel to the X-axis, as shown by arrow RX in FIG. 15. Then,main controller 20 acquires measurement values y_(A1) and y_(C1) ofencoders 70A and 70C, configured by Y scales 39Y₁ and 39Y₂ and Y heads64 _(A3) and 64 _(C4) that face Y scales 39Y₁ and 39Y₂, respectively.

Then, based on measurement values y_(A0), y_(C0), and y_(A1), y_(C1) ofencoders 70A and 70C acquired above, and angle φ above, main controller20 computes the so-called Abbe offset quantities h_(A) and h_(C) of Yscales 39Y₁ and 39Y₂.

In this case, because φ is a very small angle, sin φ=φ and cos φ=1 arevalid.

h _(A)=(y _(A1) −y _(A0))/φ  (24)

h _(C)=(y _(C1) −y _(C0))/φ  (25)

Next, after adjusting the pitching amount of wafer stage WST so thatpitching amount Δθx becomes zero, main controller 20 drives wafer stageWST if necessary in the X-axis direction, and makes a predetermined Xhead 66 of head units 62B and 62D face the specific area on X scales39X₁ and 39X₂ where each X head 66 had faced when acquiring the stageposition induced error correction information in the previousdescription.

Next, main controller 20 performs a calculation of formula (6)previously described, using the output of Z interferometers 43A and 43Bpreviously described, and in the case displacement (rolling amount) Δθyof wafer stage WST in the θy direction with respect to the XY plane isnot zero, main controller 20 tilts wafer stage WST around an axis thatpasses the exposure center and is parallel to the Y-axis so that rollingamount Δθy becomes zero. Then, after such adjustment of the rollingamount of wafer stage WST, main controller 20 acquires measurementvalues x_(B0) and x_(D0) of encoders 70B and 70D, configured by X scales39X₁ and 39X₂ and each X head 66, respectively.

Next, main controller 20 tilts wafer stage WST at angle φ around theaxis that passes the exposure center and is parallel to the Y-axis,based on the output of Z interferometers 43A and 43B, and acquiresmeasurement values X_(B1) and X_(D1) of encoders 70B and 70D, configuredby X scales 39X₁ and 39X₂ and each X head 66, respectively.

Then, based on measurement values X_(B0), X_(D0), and X_(B1), X_(D1) ofencoders 70B and 70D acquired above, and angle φ above, main controller20 computes the so-called Abbe offset quantities h_(B) and h_(D) of Xscales 39X₁ and 39X₂. In this case, φ is a very small angle.

h _(B)=(x _(B1) −x _(B0))/φ  (26)

h _(D)=(x _(D1) −x _(D0))/φ  (27)

As it can be seen from formulas (24) and (25) above, when the pitchingamount of wafer stage WST is expressed φx, then Abbe errors ΔA_(A) andΔA_(C) of Y encoders 70A and 70C that accompany the pitching of waferstage WST can be expressed as in the following formulas (28) and (29).

ΔA _(A) =h _(A) *φx  (28)

ΔA _(C) =h _(C) *φx  (29)

As it can be seen from formulas (26) and (27) above, when the rollingamount of wafer stage WST is expressed φy, then Abbe errors ΔA_(B) andΔA_(D) of X encoders 70B and 70D that accompany the rolling of waferstage WST can be expressed as in the following formulas (30) and (31).

ΔA _(B) =h _(B) *φy  (30)

ΔA _(D) =h _(D) *φy  (31)

Main controller 20 stores the quantities h_(A) to h_(D) or formulas (28)to (31) obtained in the manner described above in memory 34.Accordingly, on the actual position control of wafer stage WST such asduring lot processing and the like, main controller 20 is able to drive(perform position control of) wafer stage WST with high precision in anarbitrary direction within the XY plane while correcting the Abbe errorsincluded in the positional information of wafer stage WST within the XYplane (the movement plane) measured by the encoder system, or, morespecifically, measurement errors of Y encoders 70A and 70C correspondingto the pitching amount of wafer stage WST caused by the Abbe offsetquantities of the surface of Y scales 39Y₁ and 39Y₂ (the gratingsurface) with respect to the reference surface previously described, ormeasurement errors of X encoders 70B and 70D corresponding to therolling amount of wafer stage WST caused by the Abbe offset quantitiesof the surface of X scales 39X₁ and 39X₂ (the grating surface) withrespect to the reference surface previously described.

Now, in the case the optical axis of the heads of the encodersubstantially coincides with the Z-axis, and the pitching amount,rolling amount, and yawing amount of wafer stage WST are all zero, as itis obvious from formulas (22) and (23) above, measurement errors of theencoder described above due to the attitude of wafer table WTB are notsupposed to occur, however, even in such a case, the measurement errorsof the encoder are not actually zero. This is because the surface of Yscales 39Y₁ and 39Y₂, and X scales 39X₁ and 39X₂ (the surface of thesecond water repellent plate 28 b) is not an ideal plane, and issomewhat uneven. When the surface of the scale (to be more precise, thediffraction grating surface, and including the surface of a cover glassin the case the diffraction grating is covered with the cover glass) isuneven, the scale surface will be displaced in the Z-axis direction(move vertically), or be inclined with respect to the heads of theencoder even in the case when wafer stage WST moves along a surfaceparallel to the XY plane. This consequently means none other that arelative motion occurs in the direction besides the measurementdirection between the head and the scale, and as it has already beendescribed, such a relative motion becomes a cause of the measurementerror.

Further, as shown in FIG. 16, for example, in the case of measuring aplurality of measurement points P₁ and P₂ on the same scale 39 x using aplurality of heads 66A and 66B, when the tilt of the optical axis of theplurality of heads 66A and 66B is different and there is also anunevenness (including inclination) to the surface of scale 39X, as isobvious from ΔX_(a)≠ΔX_(B) shown in FIG. 16, the influence that theunevenness has on the measurement values will differ for each headdepending on the tilt difference. Accordingly, in order to remove suchdifference in the influence, it will be necessary to obtain theunevenness of the surface of scale 39X. The unevenness of the surface ofscale 39 x may be measured, for example, using a measurement unitbesides the encoder such as the Z sensor previously described, however,in such a case, because the measurement accuracy of the unevenness isset according to the measurement resolution of the measurement unit, inorder to measure the unevenness with high precision, a possibility mayoccur of having to use a sensor that has higher precision and anexpensive sensor must become use than the sensor which is necessary foran original purpose as a Z sensor to measure unevenness in highaccuracy.

Therefore, in the embodiment, a method of measuring the unevenness ofthe surface of a scale using the encoder system itself is employed.Following is a description of the method.

As shown in a graph (an error characteristics curve) of FIG. 12, whichshows a change characteristic of the measurement values of the encoder(a head) corresponding to the Z leveling of wafer stage WST previouslydescribed, only one point can be found in the Z-axis direction for eachencoder head where the head has no sensibility to the tilt operation ofwafer stage WST, or more specifically, a singular point where themeasurement error of the encoder becomes zero regardless of the angle ofinclination of wafer stage WST to the XY plane. If this point can befound by moving wafer stage WST similarly as when acquiring the stageposition induced error correction information previously described, thepoint (a Z position) can be positioned the singular point with respectto the encoder head. If such operation to find the singular point isperformed on a plurality of measurement points on the scale, the shape(unevenness) of the surface of the scale can be obtained.

(a) Therefore, main controller 20 first of all drives wafer stage WSTvia stage drive system 124, while monitoring the measurement values of Yinterferometer 16 of interferometer system 118, X interferometer 126,and Z interferometers 43A and 43B, and as shown in FIG. 17, makes anarbitrary Y head of head unit 62A, such as for example, Y head 64, inFIG. 17, face the vicinity of the end section of Y scale 39Y₁ on the +Yside. Then, main controller 20 changes the pitching amount (θx rotationquantity) of wafer stage WST at the position in at least two stages asis previously described, and in a state where the attitude of waferstage WST at the time of change is maintained for every change, maincontroller 20 scans (moves) wafer stage WST in the Z-axis direction in apredetermined stroke range while irradiating a detection light on apoint of Y scale 39Y₁ subject to measurement from Y head 64 _(A2), andsamples the measurement results of Y head 64 _(A2) (encoder 70A) thatfaces Y scale 39Y₁ during the scan (movement). Incidentally, thesampling above is performed while maintaining the yawing amount (androlling amount) of wafer stage WST at zero.

Then, by performing a predetermined operation based on the samplingresults, main controller 20 obtains an error characteristics curve(refer to FIG. 12) at the point described above subject to themeasurement of encoder 70A corresponding to the Z position of waferstage WST for a plurality of attitudes, and sets the intersecting pointof the plurality of error characteristics curves, or more specifically,sets the point where the measurement error of encoder 70A above becomeszero regardless of the angle of inclination of wafer stage WST withrespect to the XY plane as the singular point at the measurement point,and obtains Z positional information z₁ (refer to FIG. 18A) of thesingular point.

(b) Next, main controller 20 steps wafer stage WST in the +Y directionby a predetermined amount via stage drive system 124 while maintainingthe pitching amount and rolling amount of wafer stage WST at zero, whilemonitoring the measurement values of Y interferometer 16 ofinterferometer system 118, X interferometer 126, and Z interferometers43A and 43B. This step movement is performed at a speed slow enough sothat measurement errors caused by air fluctuation of the interferometerscan be ignored.(c) Then, at a position after the step movement, as in (a) above, maincontroller 20 obtains a Z positional information z_(p) (in this case,p=2) of the singular point of encoder 70A above at the position.

After this operation, by repeating the operations similar to the onesdescribed in (b) and (c) above, main controller 20 obtains a Zpositional information z_(p) (p=2, 3 . . . , i, . . . k, . . . n) in aplurality of (e.g. n−1) measurement points set at a predeterminedinterval in the Y-axis direction on scale 39Y₁.

FIG. 18B shows a z positional information z_(i) of the singular point atthe i-th measurement point that was obtained in the manner describedabove, and FIG. 18C shows a z positional information z_(k) of thesingular point at the k^(th) measurement point.

(d) Then, based on Z positional information z₁, z₂, . . . z, of thesingular point obtained for each of the plurality of measurement pointsabove, main controller 20 obtains the unevenness of scale 39Y₁. As shownin FIG. 18D, if one end of a double-sided arrow showing Z position z, ofthe singular point in each measurement point on scale 39Y₁ is made tocoincide with a predetermined reference line, the curve which links theother end of each double-sided arrow indicates the shape of the surface(unevenness) of scale 39Y₁. Accordingly, main controller 20 obtainsfunction z=f₁(y) that expresses this unevenness by performing curvefitting (a least square approximation) on the point at the other end ofeach double-sided arrow, and is stored in memory 34. Incidentally, y isa Y-coordinate of wafer stage WST measured with Y interferometer 16.(e) In a similar manner described above, main controller 20 obtainsfunction z=f₂(y) that expresses the unevenness of Y scale 39Y₂, functionz=g₁(x) that expresses the unevenness of X scale 39X₁, and, functionz=g₂(x) that expresses the unevenness of X scale 39X₂, respectively, andstores them in memory 34. Incidentally, x an X-coordinate of wafer stageWST measured with X interferometer 126.

In this case, at each measurement point on each scale, when an errorcharacteristics curve whose measurement error always becomes zero isobtained regardless of the change of Z in the case of obtaining theerror characteristics curve (refer to FIG. 12) described above, thepitching amount (or rolling amount) of wafer stage WST at the point whenthe error characteristics curve was obtained corresponds to an inclinedquantity of the scale surface at the measurement point. Accordingly, inthe method above, information on inclination at each measurement pointcan also be obtained, in addition to the height information of the scalesurface. This arrangement allows fitting with higher precision when thecurve fitting described above is performed.

Now, the scale of the encoder lacks in mechanical long-term stability,such as in the diffraction grating deforming due to thermal expansion orother factors by the passage of use time, or the pitch of thediffraction grating changing partially or entirely. Therefore, becausethe errors included in the measurement values grow larger with thepassage of use time, it becomes necessary to correct the errors.Hereinafter, an acquisition operation of correction information of thegrating pitch and of correction information of the grating deformationperformed in exposure apparatus 100 of the embodiment will be described,based on FIG. 19.

In FIG. 19, measurement beams B4₁ and B4₂ are arranged symmetric tostraight line LV previously described, and the substantial measurementaxis of Y interferometer 16 coincides with straight line LV, whichpasses through the optical axis of projection optical system PL and isparallel to the Y-axis direction. Therefore, according to Yinterferometer 16, the Y position of wafer table WTB can be measuredwithout Abbe error. Similarly, measurement beams B5₁ and B5₂ arearranged symmetric to straight line LH previously described, and thesubstantial measurement axis of X interferometer 126 coincides withstraight line LH, which passes through the optical axis of projectionoptical system PL and is parallel to the X-axis direction. Therefore,according to X interferometer 126, the X position of wafer table WTB canbe measured without Abbe error.

First of all, an acquisition operation of correction information of thedeformation (curve of the grid line) of the grid line of the X scale,and correction information of the grating pitch of the Y scale will bedescribed. In this case, to simplify the description, reflection surface17 b is to be an ideal plane. Further, prior to this acquisitionoperation, a measurement of the unevenness information of the surface ofeach scale described above is performed, and function z=f₁(y) thatexpresses the unevenness of Y scale 39Y₁, function z=f₂(y) thatexpresses the unevenness of Y scale 39Y₂, function z=g₁(x) thatexpresses the unevenness of X scale 39X₁, and function z=g₂(x) thatexpresses the unevenness of X scale 39X₂, are to be stored in memory 34.

First of all, main controller 20 reads function z=f₁(y), functionz=f₂(y), function z=g₁(x) and function z=g₂(x) stored in memory 34 intothe internal memory.

Next, at a speed low enough so that the short-term variation of themeasurement values of Y interferometer 16 can be ignored and also in astate where the measurement value of X interferometer 126 is fixed to apredetermined value, main controller 20 moves wafer stage WST based onthe measurement values of Y interferometer 16, and Z interferometers 43Aand 43B, for example, in at least one direction of the +Y direction andthe −Y-direction with in the effective stroke range mentioned earlier asis indicated by arrow F and F′ in FIG. 19, in a state where the pitchingamount, the rolling amount, and the yawing amount are all maintained atzero. During this movement, while correcting the measurement values (theoutput) of Y linear encoders 70A and 70C using the function z=f₁(y) andfunction z=f₂(y) described above, respectively, main controller 20 takesin the measurement values after the correction and the measurementvalues (or to be more precise, measurement values of interferometerbeams B4₁ and B4₂) of Y interferometer 16 at a predetermined samplinginterval, and based on each measurement value that has been taken in,obtains a relation between the measurement values of Y linear encoders70A and 70C (output of encoder 70A—the measurement values correspondingto function f₁(y), output of encoder 70C—the measurement valuescorresponding to function f₂(y)) and the measurement values of Yinterferometer 16. More specifically, in the manner described above,main controller 20 obtains a grating pitch (the distance betweenadjacent grid lines) of Y scales 39Y₁ and 39Y₂ which are sequentiallyplaced opposing head units 62A and 62C with the movement of wafer stageWST and correction information of the grating pitch. As the correctioninformation of the grating pitch, for example, in the case a horizontalaxis shows the measurement values of the interferometer and a verticalaxis shows the measurement values (the measurement values whose errorsdue to the unevenness of the scale surface has been corrected) of theencoder, a correction map which shows the relation between the two usinga curve can be obtained. Because the measurement values of Yinterferometer 16 in this case are obtained when wafer stage WST wasscanned at an extremely low speed as was previously described, themeasurement values hardly include any short-term variation errors due toair fluctuation, as well as long-term variation errors, and it can besaid that the measurement values are accurate values in which the errorscan be ignored.

Further, during the movement of wafer stage WST described above, bystatistically processing the measurement values (the measurement valuesof X linear encoders 70B and 70D) obtained from a plurality of X heads66 of head units 62B and 62D placed sequentially opposing X scales 39X₁and 39X₂ with the movement, such as, for example, averaging (orperforming weighted averaging), main controller 20 also obtainscorrection information of the deformation (warp) of grid lines 37 whichsequentially face the plurality of X heads 66. This is because in thecase reflection surface 17 b is an ideal plane, the same blurringpattern should appear repeatedly in the process when wafer stage WST issent in the +Y direction or the −Y-direction, therefore, if averaging orthe like is performed on the measurement data acquired with theplurality of X heads 66, it becomes possible to precisely obtaincorrection information of the deformation (warp) of grid lines 37 whichsequentially face the plurality of X head 66.

Incidentally, in a normal case where reflection surface 17 b is not anideal plane, by measuring the unevenness (warp) of the reflectionsurface and obtaining the correction data of the curve in advance andperforming movement of wafer stage WST in the +Y direction or the−Y-direction while controlling the X position of wafer stage WST, basedon the correction data instead of fixing the measurement value of Xinterferometer 126 to the predetermined value on the movement of waferstage WST in the +Y direction or the −Y-direction described above, waferstage WST can be made to move precisely in the Y-axis direction. In thismanner, the same correction information of the grating pitch of the Yscale and the correction information of the deformation (warp) of gridlines 37 can be obtained as in the description above. Incidentally, themeasurement data acquired with the plurality of X heads 66 describedabove is a plurality of data at different location references ofreflection surface 17 b, and because X heads 66 measure deformation(warp) of the same grid line 37, there is a collateral effect of thecurve correction residual of the reflection surface being averaged andapproaching its true value (in other words, by averaging the measurementdata (curve information of grid line 37) acquired by the plurality of Xheads, the effect of the curve residual can be weakened) by theaveraging or the like described above.

Next, acquisition operations of correction information of deformation(curve of the grid lines) of the grid lines of the Y scale andcorrection information of the grating pitch of the X scale will bedescribed. In this case, to simplify the description, reflection surface17 a is to be an ideal plane. In this case, a processing as in the caseof the correction described above, but with the X-axis direction and theY-axis direction interchanged, should be performed.

More specifically, at a speed low enough so that the short-termvariation of the measurement values of X interferometer 126 can beignored and also in a state where the measurement value of Yinterferometer 16 is fixed to a predetermined value, main controller 20moves wafer stage WST based on the measurement values of Yinterferometer 16, and Z interferometers 43A and 43B, for example, in atleast one direction of the +X direction and the −X-direction with in theeffective stroke range mentioned earlier, in a state where the pitchingamount, the rolling amount, and the yawing amount are all maintained atzero. During this movement, while correcting the measurement values of Xlinear encoders 70B and of 70D using the function z=g₁(x) and functionz=g₂(x) described above, respectively, main controller 20 takes in themeasurement values after the correction and the measurement values of Xinterferometer 126 at a predetermined sampling interval, and based oneach measurement value that has been taken in, obtains a relationbetween the measurement values of X linear encoders 70B and 70D (outputof encoder 70B—the measurement values corresponding to function g₁(x),output of encoder 70D—the measurement values corresponding to functiong₂(x)) and the measurement values of X interferometer 126. Morespecifically, in the manner described above, main controller 20 obtainsa grating pitch (the distance between adjacent grid lines) of X scales39X₁ and 39X₂ which are sequentially placed opposing head units 62B and62D with the movement of wafer stage WST and the correction informationof the grating pitch. As the correction information of the gratingpitch, for example, in the case a horizontal axis shows the measurementvalues of the interferometer and a vertical axis shows the measurementvalues (the measurement values whose errors due to the unevenness of thescale surface has been corrected) of the encoder, a map which shows therelation between the two using a curve can be obtained. Because themeasurement values of X interferometer 126 in this case are obtainedwhen wafer stage WST was scanned at an extremely low speed as waspreviously described, the measurement values hardly include anyshort-term variation errors due to air fluctuation, as well as long-termvariation errors, and it can be said that the measurement values areaccurate values in which the errors can be ignored.

Further, during the movement of wafer stage WST described above, bystatistically processing the measurement values (the measurement valuesof Y linear encoders 70A and 70C) obtained from a plurality of Y heads64 of head units 62A and 62C placed sequentially opposing Y scales 39Y₁and 39Y₂ with the movement, such as, for example, averaging (orperforming weighted averaging), main controller 20 also obtainscorrection information of the deformation (warp) of grid lines 38 whichsequentially face the plurality of Y heads 64. This is because in thecase reflection surface 17 a is an ideal plane, the same blurringpattern should appear repeatedly in the process when wafer stage WST issent in the +X direction or the −X-direction, therefore, if averaging orthe like is performed on the measurement data acquired with theplurality of Y heads 64, it becomes possible to precisely obtaincorrection information of the deformation (warp) of grid lines 38 whichsequentially face the plurality of Y head 64.

Incidentally, in a normal case where reflection surface 17 a is not anideal plane, by measuring the unevenness (warp) of the reflectionsurface and obtaining the correction data of the curve in advance andperforming movement of wafer stage WST in the +X direction or the−X-direction while controlling the Y position of wafer stage WST, basedon the correction data instead of fixing the measurement value of Yinterferometer 16 to the predetermined value on the movement of waferstage WST in the +X direction or the −X-direction described above, waferstage WST can be made to move precisely in the X-axis direction. In thismanner, the same correction information of the grating pitch of the Xscale and the correction information of the deformation (warp) of gridlines 38 can be obtained as in the description above.

As is described above, main controller 20 obtains correction informationon grating pitch of the Y scales and correction information ondeformation (warp) of grating lines 37, and correction information ongrating pitch of the X scales and correction information on deformation(warp) of grating lines 38 at each predetermined timing, for example,with respect to each lot, or the like.

And, during processing of the lot, main controller 20 performs movementcontrol of wafer stage WST in the Y-axis direction, using Y scales 39Y₁and 39Y₂ and head units 62A and 62C, or more specifically, using Ylinear encoders 70A and 70C, while correcting the measurement valuesobtained from head units 62A and 62C (more specifically, the measurementvalues of encoders 70A and 70C), based on correction information of thegrating pitch and correction information of the deformation (warp) ofgrid line 38 referred to above, stage position induced error correctioninformation corresponding to the Z position of wafer stage WST measuredby interferometer system 118, pitching amount Δθx, and yawing amountΔθz, and correction information of the Abbe error that corresponds topitching amount Δθx of wafer stage WST caused by the Abbe offsetquantity of the surface of Y scales 39Y₁ and 39Y₂. By this operation, itbecomes possible for main controller 20 to perform movement control ofwafer stage WST in the Y-axis direction with good precision using Ylinear encoders 70A and 70C, without being affected by temporal changeof the grating pitch of the Y scale and the warp of each grating (line)that make up the Y scale, without being affected by the change ofposition of wafer stage WST in the direction besides the measurementdirection (relative motion between the head and the scale in thedirection besides the measurement direction), and without being affectedby the Abbe error.

Further, during processing of the lot, main controller 20 performsmovement control of wafer stage WST in the X-axis direction, using Xscales 39X₁ and 39X₂ and head units 62B and 62D, or more specifically,using X linear encoders 70B and 70D, while correcting the measurementvalues obtained from head units 62B and 62D (more specifically, themeasurement values of encoders 70B and 70D), based on correctioninformation of the grating pitch and correction information of thedeformation (warp) of grid line 37 referred to above, stage positioninduced error correction information corresponding to the Z position ofwafer stage WST measured by interferometer system 118, rolling amountθy, and yawing amount θz, and correction information of the Abbe errorthat corresponds to rolling amount Δθy of wafer stage WST caused by theAbbe offset quantity of the surface of X scales 39X₁ and 39X₂. By thisoperation, it becomes possible for main controller 20 to performmovement control of wafer stage WST in the X-axis direction with goodprecision using X linear encoders 70B and 70D, without being affected bytemporal change of the grating pitch of the X scale and the warp of eachgrating (line) that make up the X scale, without being affected by thechange of position of wafer stage WST in the direction besides themeasurement direction (relative motion between the head and the scale inthe direction besides the measurement direction), and without beingaffected by the Abbe error.

Incidentally, in the description above, the case has been describedwhere the correction information of the grating pitch and the grid linewarp was acquired for both the Y scale and the X scale, however, thepresent invention is not limited to this, and the correction informationof the grating pitch and the grid line warp can be acquired only foreither the Y scale or the X scale, or the correction information of onlyeither the grating pitch or the grid line warp can be acquired for boththe Y scale and the X scale. For example, in the case where only theacquisition of the correction information of the warp of grid line 37 ofthe X scale is performed, wafer stage WST can be moved in the Y-axisdirection based on the measurement values of Y linear encoders 70A and70C, without necessarily using Y interferometer 16. Similarly, in thecase where only the acquisition of the correction information of thewarp of grid line 38 of the Y scale is performed, wafer stage WST can bemoved in the X-axis direction based on the measurement values of Xlinear encoders 70B and 70D, without necessarily using X interferometer126. Further, either one of the stage position induced error previouslydescribed or the measurement error (hereinafter also referred to as ascale induced error) of the encoder which occurs due to the scale (forexample, degree of flatness of the grating surface (surface smoothness)and/or grating formation error (including pitch error, grid line warpand the like) can be compensated.

Now, on actual exposure, wafer stage WST is driven by main controller 20via stage drive system 124 at a speed in which the short-term variationof the measurement values due to air fluctuation on the optical path ofthe beam of the interferometer cannot be ignored. Accordingly, itbecomes important to perform position control of wafer stage WST basedon the measurement values of the encoder system. For example, when waferstage WST is scanned in the Y-axis direction during exposure, maincontroller 20 drives stage drive system 124 based on the measurementvalues of a pair of Y heads 64 (a Y encoder) which faces Y scales 39Y₁and 39Y₂, respectively.

In doing so, in order to move wafer stage WST accurately in Y-axisdirection via wafer stage drive system 124 based on the measurementvalues of the pair of Y heads 64 (the Y encoder), it is necessary tomake sure that the measurement error caused by the measurement delaythat accompanies each detection signal (a photoelectric conversionsignal by the light receiving element) of the pair of Y heads 64propagating through the cable does not affect the position control ofwafer stage WST. Further, for example, on the stepping operation or thelike between shots of wafer stage WST performed between exposure of ashot area on wafer W and exposure of the adjacent shot area, maincontroller 20 also has to control the position of wafer stage WST in theX-axis direction, based on the measurement values of a pair of X heads66 (an X encoder) which face X scales 39X₁ and 39X₂, respectively. Inthis case, it is necessary to make sure that the measurement errorcaused by the measurement delay that accompanies each detection signal(a photoelectric conversion signal by the light receiving element) ofthe pair of X heads 66 propagating through the cable does not affect theposition control of wafer stage WST. Further, in order to expose all theshot areas on wafer W, a linkage operation between a plurality ofencoders is essential, which will be described later in the description.Accordingly, it becomes necessary to obtain the information of the delaytime that accompanies the detection signals (photoelectric conversionsignals by the light receiving element) of all the Y heads 64 and Xheads 66 in the encoder system and the pair of Y heads 64 y ₁ and 64 y ₂propagating through the cable in advance.

On the other hand, in addition to the encoder system, exposure apparatus100 of the embodiment can also measure positional information of waferstage WST in the XY plane by interferometer system 118. Morespecifically, in exposure apparatus 100, simultaneous measurement ofpositional information of wafer stage WST in the Y-axis direction usingeach Y head of the encoder system and Y interferometer 16 andsimultaneous measurement of positional information of positionalinformation of wafer stage WST in the X-axis direction using each X headof the encoder system and X interferometer 126 are possible.

Therefore, as in the following procedure, main controller 20 acquiresthe information of the delay time that accompanies the detection signals(photoelectric conversion signals by the light receiving element) of allthe Y heads 64 and X heads 66 in the encoder system and the pair of Yheads 64 y ₁ and 64 y ₂ propagating through the cable, for example,during the start-up period of the apparatus.

First of all, main controller 20 moves wafer stage WST to the positionso that one head of Y heads 64 in each head unit 62A and 62C faces Yscales 39Y₁ and 39Y₂, respectively. Next, main controller 20 driveswafer stage WST at a predetermined speed, such as, for example, at aspeed as in the scanning exposure, in the +Y direction or the−Y-direction, while controlling the X position of wafer stage WST basedon Y interferometer 16, X interferometer 126, and the warp correctiondata of reflection surface 17 b, and also in a state where the pitchingamount, the rolling amount, and the yawing amount are all maintained atzero, based on the measurement values of Y interferometer 16 and Zinterferometers 43A and 43B. During this drive, main controller 20 takesin detection signals from the two Y heads 64 that face Y scales 39Y₁ and39Y₂, and an output signal of Y interferometer 16 simultaneously and ata predetermined sampling interval, in a storage unit, such as, forexample, memory 34.

As a result of this, for example, an output signal C1 of Yinterferometer 16 and a detection signal C2 of each Y head 64 bothexpressed in a sine curve are obtained, as shown in FIG. 20. In FIG. 20,the horizontal axis shows time t, and the vertical axis shows signalintensity I. Incidentally, FIG. 20 shows both signals after havingnormalized at least one of the signals so that the peak value and thebottom value of both signals C1 and C2 become the same value.

Then, main controller 20 obtains intersecting points Q1 and Q2 of astraight line parallel to the vertical axis shown in FIG. 20 and bothsignals C1 and C2, obtains distance (difference in intensity) ΔI ofpoints Q1 and Q2, and then multiplies a predetermined coefficient γ tointensity difference ΔI and obtains a delay time δ of each Y head 64that accompanies signal C2 propagating through the cable, with signal C1serving as a reference. In this case, coefficient γ is a coefficient forconverting difference ΔI of intensity obtained by experiment or the likein advance into delay time δ.

In this case, as a matter of course, main controller 20 obtains delaytime δ for each of the two Y heads 64 that respectively oppose Y scales39Y₁ and 39Y₂.

Next, main controller 20 moves wafer stage WST in the −X-direction (orthe +X direction) only by a distance to the adjacent Y head, and in aprocedure similar to the description above, main controller 20 obtainsdelay time δ for each of the two Y heads 64 that respectively oppose Yscales 39Y₁ and 39Y₂. Hereinafter, main controller 20 repeats the sameprocedure as in the description above, and obtains delay time δ of allthe Y heads 64, and Y heads 64 y ₁ and 64 y ₂. Incidentally, in thedescription above, delay time δ was obtained at a time with two Y headsas a set, however, the present invention is not limited to this, anddelay time δ can be obtained for each Y head in the same procedure as inthe description above.

Further, in the case of obtaining information of the delay time thataccompanies the detection signals (photoelectric conversion signals bythe light receiving element) of each X head 66 in the encoder systempropagating through the cable, main controller 20 performs a processingin which the X-axis direction and the Y-axis direction are interchangedin the case of the correction described above. Incidentally, details onthis processing will be omitted. In the manner described above, maincontroller 20 obtains the information of delay time that accompanies thepropagation of the detection signals of each Y head through the cablewhich uses the measurement values of Y interferometer 16 as a reference,and the information of delay time that accompanies the propagation ofthe detection signals of each X head through the cable which uses themeasurement values of X interferometer 126 as a reference, respectively,and stores the information in memory 34.

Next, an example of a correction method of a measurement error in anencoder caused by a measurement delay that accompanies the detectionsignals of each head propagating through the cable is described,referring to FIG. 21. FIG. 21 shows a temporal change curve y=y(t) thatindicates an example of a temporal change of a position in the Y-axisdirection of wafer stage WST which is decelerating at a predeterminedacceleration (deceleration) from a predetermined speed v₀, and anapproximation straight line y=y_(cal)(t), which is used to correct themeasurement error. In this case, temporal change curve y=y(t) is a curve(a curve which is a least squares approximation of the measurementvalues of Y interferometer 16 obtained at a predetermined measurementsampling interval) showing a change of position of wafer stage WST inthe Y-axis direction measured by a measurement unit, Y interferometer 16in this case, which serves as a reference for delay time δ thataccompanies the propagation of the detection signals of each Y headthrough the cable. Approximation straight line y=y_(cal)(t) is astraight line that joins together point S1 and point S2 on temporalchange curve y=y(t). When the current time is expressed as t, point S1is a point corresponding to the latest measurement values of the Yencoder (Y head) that main controller 20 acquires at current time t,located on temporal change curve y=y(t) at a time (t−δ), which isearlier than the current time by only delay time δ. Further, point S2 isa point corresponding to the measurement values of the Y encoder (Yhead) that main controller 20 has acquired at time (t−Δt), which isearlier than current time t by one control sampling interval Δt (Δt, forexample, is 96 μs), or more specifically, a point corresponding to themeasurement values of the previous Y encoder (Y head), located ontemporal change curve y=y(t) at time (t−Δt−δ). Accordingly, maincontroller 20 can compute approximation straight line y=y_(cal)(t),based on the latest measurement values of the Y encoder (Y head) whichmain controller 20 acquires at current time t and the measurement valuesof the previous Y encoder (Y head).

In this case, approximation straight line y=y_(cal)(t) can be expressedas in formula (32) below.

$\begin{matrix}{y = {{y_{cal}(t)} = {{y\left( {t - \delta} \right)} + {\frac{{y\left( {t - \delta} \right)} - {y\left( {t - \delta - {\Delta \; t}} \right)}}{\Delta \; t}\delta}}}} & (32)\end{matrix}$

Further, because temporal change curve y=y(t) is a curve that shows anexample of a position change of wafer stage WST in the Y-axis directiondecelerating at a predetermined acceleration (deceleration) a from apredetermined speed v₀, it can be expressed, as an example, as informula (33) below.

y=y(t)=v ₀ t−1/2at ²  (33)

Accordingly, the correction error shown in FIG. 21, or morespecifically, a difference (y_(cal)(t)−y(t)) between y=y(t) andy=y_(cal)(t) at current time t can be expressed as in formula (34)below.

$\begin{matrix}{{{y_{cal}(t)} - {y(t)}} = {\frac{a\; {\delta \left( {\delta + {\Delta \; t}} \right)}}{2} \cong \frac{a\; \delta \; \Delta \; t}{2}}} & (34)\end{matrix}$

In the case of deceleration (acceleration) a −20 [m/s²], delay timeδ=100 [ns], and one control sampling interval Δt=96 [μsec], thecorrection error results to be 0.1 nm, which is a quantity that will notcause any problems for the time being. More specifically, if delay timeδ of each Y head is precisely obtained, the measurement errors of theencoder due to the measurement delay (delay time) can be correctedsoftware wise by the method described above.

More specifically, by locating points S1 and S2 on temporal change curvey=y(t) at time t and time (t−Δt), computing the approximation straightline y=y_(cal)(t) that passes through points S1 and S2, and obtaining ay-coordinate value of a point on approximation straight liney=y_(cal)(t) at time t, based on the measurement values of each Y headof the encoder system and the measurement values which are one controlsampling interval earlier, main controller 20 can correct themeasurement errors by the measurement delay that accompanies thedetection signals of each Y head propagating through the cable, and cancorrect the influence of the measurement delay of each Y head of theencoder system.

Further, main controller 20 can also correct the influence of themeasurement delaying (delay time δ) on each X head 66 of the encodersystem in a manner similar to the description above.

As other generation factors of measurement errors, temperaturefluctuation (air fluctuation) of the atmosphere on the beam optical pathcan be considered. Phase difference φ between the two return beams LB₁and LB₂ depend on optical path difference ΔL of the two beams, accordingto the first term on the right-hand side of formula (16). Suppose thatwavelength λ of the light changes to λ+Δλ by air fluctuation. By minutechange Δλ of this wavelength, the phase difference changes by minuteamount Δφ=2πΔLΔλ/λ². In this case, when the wavelength of light λ=1 μmand minute change Δλ=1 nm, then phase change Δφ=2π with respect tooptical path difference ΔL=1 mm. This phase change is equivalent to 1when it is converted into a count value of the encoder. Further, when itis converted into displacement, it is equivalent to p/2 (n_(b)−n_(a)).Accordingly, if n_(b)=−n_(a)=1, in the case of p=1 μm, a measurementerror of 0.25 μm will occur.

In the actual encoder, because the optical path length of the two beamswhich are made to interfere is extremely short, wavelength change Δλdueto the air fluctuation is extremely small. Furthermore, optical pathdifference ΔL is designed to be approximately 0, in an ideal state wherethe optical axis is orthogonal to the reflection surface. Therefore, themeasurement errors due to the air fluctuation can be substantiallyignored. The fluctuation is remarkably small when compared with theinterferometer, and is superior in short-term stability.

In exposure apparatus 100 of the embodiment, for example, at the time ofstart-up of the apparatus, main controller 20 can perform a series ofcalibration processing described earlier, or more specifically, A.acquisition processing of the stage position induced error correctioninformation, B. head position calibration processing, C. calibrationprocessing to obtain Abbe offset quantity, D. processing for obtainingthe shape (unevenness) of the surface of the scale, E. acquisitionprocessing of correction information of the grating pitch of the scaleand the correction information of the grating deformation, and F.acquisition processing of the correction information of the measurementerrors due to the measurement delay, a plurality of times, or repeatedin the order previously described or in a different order. On thisrepetition, the various calibrations from the second time onward can beperformed, using the various information that has been measured untilthe previous time.

For example, on the acquisition processing of the stage position inducederror correction information described above, for example, the pitching(or the rolling) of wafer table WTB (wafer stage WST) has to be adjustedby making wafer stage WST perform a θx rotation (or a θy rotation)around a point where Z position z=0 serves as a center, and as thepremise, the Abbe offset quantity previously described of Y scales 39Y₁and 39Y₂ (or, X scales 39X₁ and 39X₂) will have to be known. Therefore,in the first acquisition process of the stage position induced errorcorrection information, A. acquisition processing of the stage positioninduced error correction information can be performed in the proceduredescribed above, using design values of Y scales 39Y₁ and 39Y₂ (or, Xscale 39X₁ and 39X₂) as the Abbe offset quantity, and then, afterperforming B. head position calibration processing and C. calibrationprocessing to obtain Abbe offset quantity, D. processing for obtainingthe shape (unevenness) of the surface of the scale and E. acquisitionprocessing of correction information of the grating pitch of the scaleand the correction information of the grating deformation can beperformed, and then, when the second A. acquisition process of the stageposition induced error correction information is performed, wafer stageWST can be made to perform a θx rotation (or a θy rotation) around apoint where Z position z=0 serves as a center, based on the Abbe offsetquantity which is actually obtained in the manner described above, andthe stage position induced error correction information can be acquiredin the procedure previously described. By the processing describedabove, it becomes possible to acquire the stage position induced errorcorrection information that is not affected by the errors to the designvalues of the Abbe offset quantity in the second measurement.

Next, a switching process of the encoder used for position control ofwafer stage WST in the XY plane that is executed during the actualprocessing or the like, or more specifically, a linkage process betweena plurality of encoders will be described, after processing such as theacquisition of the stage position induced error correction information,unevenness measurement of the surface of the scale, the acquisition ofcorrection information of the grating pitch of the scale and thecorrection information of the grating deformation, and the acquisitionof the Abbe offset quantity of the scale surface and the like areperformed in advance.

In this case, first of all, prior to describing the linkage process ofthe plurality of encoders, a concrete method of converting the correctedmeasurement values of the encoder into the position of wafer stage WST,which is the premise, will be described, using FIGS. 22A and 22B. Inthis case, in order to simplify the description, the degrees of freedomof wafer stage WST is to be three degrees of freedom (X, Y, and θz).

FIG. 22A shows a reference state where wafer stage WST is at the originof coordinates (X, Y, θz)=(0, 0, 0). From this reference state, waferstage WST is driven within a range where encoders (Y heads) Enc1 andEnc2 and encoder (X head) Enc3 do not move away from the scanning areasof their opposing scales 39Y₁ and 39Y₂ and 39X₁. The state where waferstage WST is moved to position (X, Y, θz) in the manner described aboveis shown in FIG. 22B.

Here, supposing that the position coordinates (X, Y) of the measurementpoints of encoders Enc1, Enc2, and Enc3 on the XY coordinate system are(p₁, q₁), (p₂, q₂), and (p₃, q₃), respectively. Then, as X coordinatevalues p₁ and p₂ of encoders Enc1 and Enc2 and Y coordinate values q₃ ofEnc3, the positional information which was acquired in the case of thecalibration of the head position described earlier is read from memory34 and is used, whereas as Y coordinate values q₁ and q₂ of encodersEnc1 and Enc2 and X coordinate values p₃ of Enc3, the positionalinformation of design values is read from memory 34 and is used.

The X head and the Y head respectively measure the relative distancefrom central axes LL and LW of wafer stage WST. Accordingly, measurementvalues C_(X) and C_(Y) of the X head and the Y head can be expressed,respectively, as in the following formulas (35a) and (35b).

C _(X) =r′*ex′  (35a)

C _(Y) =r′*ey′  (35b)

In this case, ex′ and ey′ are X′ and Y′ unit vectors in a relativecoordinate system (X′, Y′,θz′) set on wafer stage WST, and have arelation as in the following Y formula (36) with ex and ey, which are X,Y unit vectors in a reference coordinate system (X, Y, θz).

$\begin{matrix}{\begin{pmatrix}{ex}^{\prime} \\{ey}^{\prime}\end{pmatrix} = {\begin{pmatrix}{\cos \; \theta \; z} & {\sin \; \theta \; z} \\{{- \sin}\; \theta \; z} & {\cos \; \theta \; z}\end{pmatrix}\begin{pmatrix}{ex} \\{ey}\end{pmatrix}}} & (36)\end{matrix}$

Further, r′ is a position vector of the encoder in the relativecoordinate system, and r′ is given r′=r−(O′−O), using position vectorr=(p, q) in the reference coordinate system. Accordingly, formulas (35a)and (35b) can be rewritten as in the next formulas (37a) and (37b).

C _(X)=(p−X)cos θz+(q−Y)sin θz  (37a)

C _(Y)=−(p−X)sin θz+(q−Y)cos θz  (37b)

Accordingly, as shown in FIG. 22B, when wafer stage WST is located atthe coordinate (X, Y, θz), the measurement values of three encoders canbe expressed theoretically in the next formulas (38a) to (38c) (alsoreferred to as a relationship of the affine transformation).

C ₁=−(p ₁ −X)sin θz+(q ₁ −Y)cos θz  (38a)

C ₂−(p ₂ −X)sin θz+(q ₂ −Y)cos θz  (38b)

C ₃=(p ₃ −X)cos θz+(q ₃ −Y)sin θz  (38c)

Incidentally, in the reference state of FIG. 22A, according tosimultaneous formulas (38a) to (38c), C₁=q₁, C₂=q₂, and C₃=p₃.Accordingly, in the reference state, if the measurement values of thethree encoders Enc1, Enc2, and Enc3 are initialized to q₁, q₂, and p₃respectively, then the three encoders will show theoretical values givenby formulas (38a) to (38c) with respect to displacement (X, Y, θz) ofwafer stage WST from then onward.

In simultaneous formulas (38a) to (38c), three formulas are given to thethree variables (X, Y, θz). Accordingly, if dependent variables C₁, C₂,and C₃ are given in the simultaneous formulas (38a) to (38c), variablesX, Y, and θz can be obtained. In this case, when approximation sin·θz≈θzis applied, or even if an approximation of a higher order is applied,the formulas can be solved easily. Accordingly, the position of waferstage WST (X, Y, θz) can be computed from measurement values C₁, C₂, andC₃ of the encoder.

In exposure apparatus 100 of the embodiment which is configured in themanner described above, because the placement of the X scales and Yscales on wafer table WTB and the arrangement of the X heads and Y headswhich were described above were employed, in the effective stroke range(more specifically, in the embodiment, the range in which the stagemoves for alignment and exposure operation) of wafer stage WST, at leastone X head 66 in the total of 18 X heads belonging to head units 62B and62D must face at least one of X scale 39X₁ and 39X₂, and at least one Yhead 64 each, or Y head 64 y ₁ and 64 y ₂ belonging to head units 62Aand 62C, also respectively face Y scales 39Y₁ and 39Y₂, respectively, asillustrated in FIGS. 23A and 23B. That is, at least one each of thecorresponding heads is made to face at least the three out of the fourscales.

Incidentally, in FIGS. 23A and 23B, the head which faces thecorresponding X scale or Y scale is shown surrounded in a circle.

Therefore, in the effective stroke range of wafer stage WST referred toearlier, by controlling each motor that configures stage drive system124, based on at least a total of three measurement values of theencoders, which are encoders 70A and 70C, and at least one of encoders70B and 70D, main controller 20 can control positional information(including rotation in the θz direction) of wafer stage WST in the XYplane with high accuracy. Because the effect of the air fluctuation thatthe measurement values of encoder 70A to 70D receive is small enough sothat it can be ignored when compared with an interferometer, theshort-term stability of the measurement affected by the air fluctuationis remarkably good when compared with the interferometer.

Further, when wafer stage WST is driven in the X-axis direction as isshown by an outlined arrow in FIG. 23A, Y heads 64 that measure theposition of wafer stage WST in the Y-axis direction are sequentiallyswitched, as is indicated by arrows e₁ and e₂ in the drawing, to theadjacent Y heads 64. For example, the heads are switched from Y heads 64surrounded by a solid circle to Y heads 64 that are surrounded by adotted circle. Therefore, before or after this switching, linkageprocess of the measurement values which will be described later on isperformed.

Further, when wafer stage WST is driven in the Y-axis direction as isshown by an outlined arrow in FIG. 23B, X heads 66 that measure theposition of wafer stage WST in the X-axis direction are sequentiallyswitched to the adjacent X heads 66. For example, the heads are switchedfrom X heads 66 surrounded by a solid circle to X heads 66 that aresurrounded by a dotted circle. Therefore, before or after thisswitching, linkage process of the measurement values is performed.

The switching procedure of will now be described here, based on FIGS.24A to 24E, with the switching from Y heads 64 ₃ to 64 ₄ shown by arrowe₁ in FIG. 23A serving as an example.

In FIG. 24A, a state before the switching is shown. In this state, Yhead 64 ₃ facing the scanning area (the area where the diffractiongrating is arranged) on Y scale 39Y₂ is operating, and Y head 64 ₄ whichhas moved away from the scanning area is suspended. The operating headis indicated here, using a solid black circle, and the suspended head isindicated by an outlined circle. Then, main controller 20 monitors themeasurement values of Y head 64 ₃ which is operating. The head whosemeasurement values are monitored, here, is shown in a double rectangularframe.

Then, wafer stage WST moves in the +X direction. Accordingly, Y scale39Y₂ is displaced to the right. In this case, in the embodiment, as ispreviously described, the distance between the two adjacent Y heads isset smaller than the effective width (width of the scanning area) of Yscale 39Y₂ in the X-axis direction. Accordingly, as shown in FIG. 24B, astate occurs where Y heads 64 ₃ and 64 ₄ face the scanning area of Yscale 39Y₂. Therefore, main controller 20 makes sure that Y head 64 ₄,which is suspended, has faced the scanning area along with Y head 64 ₃that is operating, and then activates the suspended Y head 64 ₄.However, main controller 20 does not yet start monitoring themeasurement values at this point.

Next, as shown in FIG. 24C, while Y head 64 ₃, which will be suspendedlater faces the scanning area, main controller 20 computes a referenceposition of Y head 64 ₄, which has been restored, from the measurementvalues of the active encoder heads including Y head 64 ₃. Then, maincontroller 20 sets the reference position as an initial value of themeasurement value of Y head 64 ₄. Incidentally, details on thecomputation of the reference position and the setting of the initialvalue will be described later in the description.

Main controller 20 switches the encoder head whose measurement valuesare monitored from Y head 64 ₃ to Y head 64 ₄ simultaneously with thesetting of the initial value above. After the switching has beencompleted, main controller 20 suspends the operation of Y head 64 ₃before it moves off the scanning area as shown in FIG. 24D. By theoperation described above, all the operations of switching the encoderheads are completed, and hereinafter, as shown in FIG. 24E, themeasurement values of Y head 64 ₄ are monitored by main controller 20.

In the embodiment, the distance between adjacent Y heads 64 that headunits 62A and 62C have is, for example, 70 mm (with some exceptions),and is set smaller than the effective width (e.g. 76 mm) of the scanningarea of Y scales 39Y₁ and 39Y₂ in the X-axis direction. Further, forexample, the distance between adjacent X heads 66 that head units 62Band 62D have is, for example, 70 mm (with some exceptions), and is setsmaller than the effective width (e.g. 76 mm) of the scanning area of Xscales 39X₁ and 39X₂ in the Y-axis direction. Accordingly, the switchingoperation of Y heads 64 and X heads 66 can be performed smoothly as inthe description above.

Incidentally, in the embodiment, the range in which both adjacent headsface the scale, or more specifically, the moving distance of wafer stageWST from a state shown in FIG. 24B to a state shown in FIG. 24D, forexample, is 6 mm. And at the center, or more specifically, when waferstage WST is located at the position shown in FIG. 24C, the head thatmonitors the measurement values is switched. This switching operation iscompleted by the time the head which is to be suspended moves off thescanning area, or more specifically, while wafer stage WST moves in anarea by a distance of 3 mm during the state shown in FIG. 24C until thestate shown in FIG. 24D. For example, in the case the movement speed ofthe stage is 1 m/sec, then the switching operation of the head is to becompleted within 3 msec.

Next, the linkage process when the encoder head is switched, or morespecifically, the initial setting of the measurement values will bedescribed, focusing mainly on the operation of main controller 20.

In the embodiment, as is previously described, three encoders (the Xheads and the Y heads) constantly observe wafer stage WST within theeffective stroke range of wafer stage WST, and when the switchingprocess of the encoder is performed, four encoders will be made toobserve wafer stage WST, as shown in FIG. 25.

At the moment when the switching process (linkage) of the encoder usedfor the position control of wafer stage WST within the XY plane is to beperformed, encoders Enc1, Enc2, Enc3 and Enc4 are positioned abovescales 39Y₁, 39Y₂, 39X₁, and 39X₂, respectively, as shown in FIG. 25.When having a look at FIG. 25, it looks as though the encoder is goingto be switched from encoder Enc1 to encoder Enc4, however, as is obviousfrom the fact that the measurement direction is different in encoderEnc1 and encoder Enc4, it does not have any meaning even if themeasurement values (count values) of encoder Enc1 are given without anychanges as the initial value of the measurement values of encoder Enc4.

Therefore, in the embodiment, main controller 20 switches frommeasurement/servo by the three encoders Enc1, Enc2 and Enc3 tomeasurement/servo by the three encoders Enc2, Enc3 and Enc4. Morespecifically, as it can be seen from FIG. 25, this method is differentfrom the concept of a normal encoder linkage, and in this method thelinkage is made not from one head to another head, but from acombination of three heads (an encoder) to a combination of anotherthree heads (an encoder). Incidentally, in the three heads and anotherthree heads, the different head is not limited to one. Further, in FIG.25, encoder Enc3 was switched to encoder Enc4, however, instead ofencoder Enc4, for example, the encoder can be switched, for example, tothe encoder adjacent to encoder Enc3.

First of all, main controller 20 solves the simultaneous formulas (38a)to (38c) based on the measurement values C₁, C₂, and C₃ of encodersEnc1, Enc2, and Enc3, and computes positional information (X, Y, θz) ofwafer stage WST within the XY plane.

Next, main controller 20 substitutes X and θz computed above into theaffine transformation of the next formula (39), and determines theinitial value of the measurement values of encoder (X head) Enc4.

C ₄=(p ₄ −X)cos θz+(q ₄ −Y)sin θz  (39)

In formula (39) above, p₄ and q₄ are the X-coordinate value and theY-coordinate value at the measurement point of encoder Enc4. As Ycoordinate value q₄ of encoder Enc4, the positional information whichwas acquired on calibration of the head position previously described isread from memory 34 and is used, while as X-coordinate value p₄ ofencoder Enc4, the design position information is read from memory 34 andis used.

By giving initial value C₄ as an initial value of encoder Enc4, linkagewill be completed without any contradiction, having maintained theposition (X, Y, θz) of wafer stage WST in directions of three degree offreedom. From then onward, the following simultaneous formulas (38b) to(38d) are solved, using the measurement values C₂, C₃, and C₄ ofencoders Enc2, Enc3, and Enc4 which are used after the switching, and aposition coordinate (X, Y, θz) of wafer stage WST is computed.

C ₂=−(p ₂ −X)sin θz+(q ₂ −Y)cos θz  (38b)

C ₃=(p ₃ −X)cos θz+(q ₃ −Y)sin θz  (38c)

C ₄=(p ₄ −X)cos θz+(q ₄ −Y)sin θz  (38d)

Incidentally, in the case the fourth encoder is a Y head, simultaneousformulas (38b) (38c) (38e) that use the following theoretical formula(38e) instead of theoretical formula (38d) can be used.

C ₄=−(p ₄ −X)sin θz+(q ₄ −Y)cos θz  (38e)

However, because measurement value C₄ computed above is a measurementvalue of a corrected encoder whose measurement errors of the variousencoders previously described have been corrected, main controller 20performs inverse correction on measurement value C₄ and computes a rawvalue C₄′ which is the value before correction, and determines raw valueC₄′ as the initial value of the measurement value of encoder Enc4, usingthe stage position induced error correction information, the correctioninformation of the grating pitch of the scale (and the correctioninformation of the grating deformation), the Abbe offset quantity (theAbbe error correction information) and the like previously described.

In this case, the inverse correction refers to the processing ofcomputing measurement value C₄′ based on measurement value C₄, under thehypothesis that the measurement value of the encoder after correctingmeasurement value C₄′ is C₄, when measurement value C₄′, on which nocorrection has been performed, is corrected using the stage positioninduced error correction information, the scale induced error correctioninformation (e.g., correction information of the grating pitch of thescale (and correction information of the grating deformation), and theAbbe offset quantity (Abbe error correction information) and the like.

Now, the position control interval (control sampling interval) of waferstage WST, as an example, is 96 [μsec], however, the measurementinterval (measurement sampling interval) of an interferometer or anencoder has to be at a much higher speed. The reason why the sampling ofthe interferometer and the encoder has to be performed at a higher-speedthan the control sampling is because both the interferometer and theencoder count the intensity change (fringe) of the interference light,and when the sampling becomes rough, measurement becomes difficult.

However, with the position servo control system of wafer stage WST, thesystem updates the current position of wafer stage WST at every controlsampling interval of 96 [μsec], performs calculation to set the positionto a target position, and outputs thrust command values and the like.Accordingly, the positional information of the wafer stage is necessaryat every control sampling interval of 96 [p sec], and the positionalinformation in between the sampling intervals will not be necessary inthe position control of wafer stage WST. The interferometer and theencoder merely perform sampling at a high speed so as not to lose trackof the fringe.

Therefore, in the embodiment, at all times while wafer stage WST islocated in the effective stroke range previously described, maincontroller 20 continues to receive the measurement values (count values)from each encoder (a head) of the encoder system, regardless of whetheror not the encoder watches the scale. And, main controller 20 performsthe switching operation (linkage operation between the plurality ofencoders) previously described, in synchronization with the timing ofthe position control of the wafer stage performed every 96 [μsec]. Insuch an arrangement, the switching operation of an electricallyhigh-speed encoder will not be required, which means that costlyhardware to realize such a high-speed switching operation does notnecessarily have to be arranged. FIG. 26 conceptually shows the timingof position control of wafer stage WST, the uptake of the count valuesof the encoder, and the switching of the encoder, which are performed inthe embodiment. In FIG. 26, reference code CSCK shows a generationtiming of a sampling clock of the position control of wafer stage WST,and reference code MSCK shows a generation timing of a measurementsampling clock of the encoder (and the interferometer). Further,reference code CH typically shows the switching (linkage) of theencoder.

Incidentally, main controller 20 performs the correction of themeasurement errors due to delay time δ for each head, each time at thegeneration timing of the sampling clock of the position control of thewafer stage, regardless of whether or not the switching of the encoderis performed. Accordingly, based on the measurement values of the threeencoders whose measurement errors due to the measurement delay have beencorrected, the position (X, Y, θz) of wafer stage WST is to becontrolled.

Now, in the description above, the switching that could be performedfrom one combination of heads (encoders) to another combination of heads(encoders), and the timing when the switching can be performed are to beknown, however, they also must be known in the actual sequence as well.It is also preferable to prepare the scheduling of the timing to carryout the linkage in advance.

Therefore, in the embodiment, main controller 20 prepares the schedulefor the switching (the switching from one combination of three heads(e.g., Enc1, Enc2, and Enc3) to another combination of three heads(e.g., Enc4, Enc2, and Enc3), and the timing of the switch) of the threeencoders (heads) which are used for measuring the positional informationof wafer stage WST in directions of three degrees of freedom (X, Y, θz)within the XY plane, based on the movement course (target track) ofwafer stage WST, and stores the scheduling result in the storage unitsuch as memory 34.

In this case, if a retry (redoing) is not considered, the contents ofthe schedule in every shot map (an exposure map) becomes constant,however, in actual practice, because a retry must be considered, it ispreferable for main controller 20 to constantly update the scheduleslightly ahead while performing the exposure operation.

Incidentally, in the embodiment above, because the description was maderelated to the principle of the switching method of the encoder used forposition control of wafer stage WST, expressions such as encoder (head)Enc1, Enc2, Enc3, and Enc4 were used, however, it goes without sayingthat head Enc1 and Enc2 indicate either Y head 64 of head units 62A and62C or a pair of Y heads 64 y ₁ and 64 y ₂, representatively, and headsEnc3 and Enc4 indicates X head 66 of head unit 62B and 62D,representatively. Further, for similar reasons, in FIGS. 22A, 22B and25, the placement of encoders (heads) Enc1, Enc2, Enc3 and the like isshown differently from the actual placement (FIG. 3 and the like).

<<Generalization of Switching and Linkage Principle>>

In the embodiment, in order to measure the position coordinates of waferstage WST in directions of three degree of freedom (X, Y, θz), among theX encoders (heads) and Y encoders (heads) that constitute encodersystems 70A to 70D, at least three heads which at least include one Xhead and at least two Y heads are constantly used. Therefore, when thehead which is to be used is switched along with the movement of waferstage WST, a method of switching from a combination of three heads toanother combination of three heads is employed, so as to continuouslylink the measurement results of the stage position before and after theswitching. This method will be referred to as a first method.

However, when considering the basic principle of the switching andlinkage process from a different point of view, it can also be viewed asa method of switching one head of the three heads that are used toanother head. This method will be referred to as a second method.Therefore, the second method will be described, with the switching andlinkage process from Y heads 64 ₃ to 64 ₄ shown in FIGS. 24A to 24E,serving as an example.

The basic procedure of the switching process is similar to the proceduredescribed above, and while both the first head 64 ₃ which will besuspended later and the second head 64 ₄ which will be newly used facethe corresponding scale 39Y₂, as shown in figure of FIG. 24A or more24E, main controller 20 executes the restoration of the second head 64 ₄and the setting of the measurement values (linkage process), and theswitching (and suspension of the first head 64 ₃) of the head monitoringthe measurement value.

When the measurement value is set (linkage process), main controller 20predicts a measurement value C_(Y4) of the second head 64 ₄ using ameasurement value C_(Y3) of the first head 64 ₃. In this case, accordingto the theoretical formula (37b), measurement values C_(Y3) and C_(Y4)of Y heads 64 ₃ and 64 ₄ follow formulas (39a) and (39b) below.

C _(Y3)=−(p ₃ −X)sin θz+(q ₃ −Y)cos θz  (39a)

C _(Y4)=−(p ₄ −X)sin θz+(q ₄ −Y)cos θz  (39b)

In this case, (p₃, q₃) and (p₄, q₄) are the X and Y setting positions(or to be more precise, the X and Y positions of the measurement points)of Y heads 64 ₃ and 64 ₄.To make it more simple, suppose that the Y setting positions of Y heads64 ₃ and 64 ₄ are equal (q₃=q₄). Under this supposition, formula (40)below can be obtained by formulas (39a) and (39b) above.

C _(Y4) =C _(Y3)+(p ₃ −p ₄)sin θz  (40)

Accordingly, by substituting the measurement value of first head 64 ₃which will be suspended later into C_(Y3) on the right-hand side offormula (40) above and obtaining C_(Y4) on the left-hand side, themeasurement value of the second head 64 ₄ which will be newly used canbe predicted.

Predicted value C_(Y4) that has been obtained is to be set as theinitial value of the measurement value of the second head 64 ₄ at aproper timing. After the setting, the first head 64 ₃ is suspended whenit moves off scale 39Y₂, which completes the switching and linkageprocess.

Incidentally, when the measurement value of the second head 64 ₄ ispredicted using formula (40) above, a value of rotation angle θz, whichis obtained from the measurement results of another head that is active,should be substituted into variable θz. In this case, another head thatis active is not limited to the first head 64 ₃ which is subject toswitching, but includes all the heads that provide the measurementresults necessary to obtain rotation angle θz. In this case, because thefirst head 64 ₃ is a head of head unit 62C, rotation angle θz can beobtained using the first head 64 ₃, and for example, one of the heads ofhead unit 62A that faces Y scale 39Y₁ during the switching. Or, a valueof rotation angle θz, which can be obtained from the measurement resultsof X interferometer 126 of interferometer system 118, Y interferometer16, or Z interferometer 43A and 43B and the like can be substituted intovariable θz.

Incidentally, the switching and linkage process between Y heads wasexplained as an example here, however, the switching and linkage processbetween X heads, and further, also the switching and linkage processbetween two heads belonging to different head units such as between theX head and the Y head can also be explained similarly as the secondmethod.

Therefore when the principle of the linkage process is generalized, themeasurement value of another head newly used is predicted so that theresults of the position measurement of wafer stage WST is linkedcontinuously before and after the switching, and the predicted value isset as the initial value of the measurement values of the second head.In this case, in order to predict the measurement values of anotherhead, theoretical formulas (37a) and (37b) and the measurement values ofthe active heads including the head which will be suspended latersubject to the switching will be used as required. However, for therotation angle in the θz direction of wafer stage WST which is necessaryon the linkage, a value which is obtained from the measurement resultsof interferometer system 118 can be used.

As is described above, even if it is premised that at least three headsare constantly used to measure the position of wafer age WST indirections of three degree of freedom (X, Y, θz) as in the precedingfirst method, if focusing on only the two heads which are direct objectsof the switching and linkage process without referring to the concreteprocedure of predicting the measurement value of another head newlyused, the observation on the second method where one head out of thethree heads used is switched to another head can be realized.

Incidentally, the description so far was made on the premise that theposition of wafer stage WST in directions of three degrees of freedom(X, Y, θz) was measured using at least three heads. However, even in thecase of measuring the position of two or more in directions of m degreesof freedom (the choice of the degrees of freedom is arbitrary) using atleast m heads, it is obvious that the observation of the second methodwhere one head out of m heads used is switched to another head can berealized, as in the description above.

Next, a description will be made in which under a specific condition, anobservation of a method (to be referred to as a third method) where acombination of two heads is switched to a combination of another twoheads can be consistently realized.

In the example above, as shown in FIGS. 24A to 24E, switching andlinkage process between heads 64 ₃ and 64 ₄ is executed, while Y heads64 ₃ and 64 ₄ each face the corresponding Y scale 39Y₂. During thisoperation, according to the placement of the scale and the head employedin exposure apparatus 100 of the embodiment, one Y head (expressed as 64_(A)) of head unit 62A faces Y scale 39Y₁ and measures relativedisplacement of Y scale 39Y₁ in the Y-axis direction.

Therefore, a switching and linkage process will be considered from afirst combination of Y heads 64 ₃ and 64 _(A) to a second combination ofY heads 64 ₄ and 64 _(A).

According to theoretical formula (37b), a measurement value C_(Y4) of Yhead 64 _(A) follows formula (39c) below.

C _(Y4)=−(p _(A) −X)sin θz+(q _(A) −Y)cos θz  (39c)

In this case, (P_(A), q_(A)) is the X and Y setting position (or to bemore precise, the X and Y positions of the measurement point) of Y head64 _(A). To make it more simple, suppose that Y setting position q_(A)of Y head 64 _(A) is equal to Y setting positions q₃ and q₄ of Y heads64 ₃ and 64 ₄ (q_(A)=q₃=q₄).

When theoretical formulas (39a) and (39c), which measurement valuesC_(Y3) and C_(YA) of Y heads 64 ₃ and 64 _(A) of the first combinationfollow, are substituted into theoretical formula (39b), whichmeasurement value C_(Y3) of Y head 64 ₄ that is newly used follows,formula (41) below is derived.

C _(Y4)=(1−c)C _(Y3) −c*C _(YA)  (41)

However, constant c=(p₃−p₄)/(q_(A)−q₃). Accordingly, by substituting themeasurement values of Y heads 64 ₃ and 64A into C_(Y3) and C_(Y4) on theright-hand side of formula (41) above and obtaining C_(Y4) on theleft-hand side, the measurement value of Y head 64 ₄ newly used can bepredicted.

Predicted value C_(Y4) that has been obtained is to be set as theinitial value of the measurement value of Y head 64 ₄ at a propertiming. After the setting, Y head 64 ₃ is suspended when it moves offscale 39Y₂, which completes the switching and linkage process.

Incidentally, according to the placement of the scale and the heademployed in exposure apparatus 100 of the embodiment, at least one Xhead 66 faces X scale 39X₁ or 39X₂ and measures the relativedisplacement in the X-axis direction. Then, according to the measurementresults of the three heads, which are one X head 66 two Y heads 64 ₃ and64 _(A), the position of wafer stage WST in directions of three degreesof freedom (X, Y, θz) is computed. However, in the example of theswitching and linkage process described above, X head 66 merely playsthe role of a spectator, and the observation of the third method where acombination of two heads, Y heads 64 ₃ and 64 _(A) is switched to acombination of another two heads, Y head 64 ₄ and 64 _(A), isconsistently realized.

Accordingly, under the premise that the use of three heads isindispensable to measure the position of wafer stage WST in directionsof three degrees of freedom (X, Y, θz), the first method was proposed asa general method of the switching and linkage process that could beapplied to every case, regardless of the placement of the scale and thehead employed in exposure apparatus 100 of the embodiment. And, based onthe concrete placement of the scale and the head employed in exposureapparatus 100 of the embodiment and the concrete procedure of thelinkage process, the observation of the third method could be realizedunder a particular condition.

Incidentally, in addition to the first method, in the switching andlinkage process of the encoder head by the second and third methodsdescribed above, the measurement value of another head to be newly usedwas predicted so that the position coordinate of wafer stage WST whichis monitored is continuously linked before and after the switching, andthis predicted value was set as an initial value for the measurementvalue of another head. Instead of the processing above, the measurementerror of another head including the measurement error generated by theswitching and linkage process can be computed and the correction datacan be made. And, while the another head is being used, the correctiondata that has been made can be used for servo drive control of waferstage WST. In this case, based on the correction data, positionalinformation of wafer stage WST measured by the another head can becorrected, or a target position of wafer stage WST for servo control canbe corrected. Furthermore, in the exposure operation, servo drivecontrol of the reticle stage is performed, following the movement ofwafer stage WST. Therefore, based on the correction data, instead ofcorrecting the servo control of wafer stage WST, the follow-up servocontrol of the reticle stage can be corrected. Further, according tothese control system, the measurement value of the head before theswitching may be set as an initial value of another head without anychanges. Incidentally, when making the correction data, not only theencoder system but also other measurement systems that the exposureapparatus in the embodiment has, such as the interferometer systems,should be appropriately used.

Next, a parallel processing operation that uses wafer stage WST andmeasurement stage MST in exposure apparatus 100 of the embodiment willbe described based on FIGS. 27 to 40. Incidentally, during the operationbelow, main controller 20 performs the open/close control of each valveof liquid supply unit 5 of local liquid immersion unit 8 and liquidrecovery unit 6 in the manner previously described, and water isconstantly filled in the space right under tip lens 191 of projectionoptical system PL. However, in the description below, for the sake ofsimplicity, the explanation related to the control of liquid supply unit5 and liquid recovery unit 6 will be omitted. Further, many drawings areused in the operation description hereinafter, however, reference codesmay or may not be given to the same member for each drawing. Morespecifically, the reference codes written are different for eachdrawing, however, such members have the same configuration regardless ofthe indication of the reference codes. The same can be said for eachdrawing used in the description so far.

FIG. 27 shows a state where exposure by the step-and-scan method isbeing performed on wafer W (in this case, as an example, the wafer is awafer midway of a certain lot (one lot contains 25 or 50 wafers)) onwafer stage WST. In this state, measurement stage MST can wait at awithdrawal position where it avoids bumping into wafer stage WST,however, in the embodiment, measurement stage MST is moving, followingwafer stage WST while keeping a predetermined distance. Therefore, whenmeasurement stage MST moves into a contact state (or a proximity state)with wafer stage WST after the exposure has been completed, the samedistance as the predetermined distance referred to above will be enoughto cover the movement distance.

During this exposure, main controller 20 controls the position(including the θz rotation) of wafer table WTB (wafer stage WST) withinthe XY plane, based on the measurement values of at least three encodersout of two X heads 66 (X encoders 70B and 70D) shown surrounded by acircle in FIG. 27 facing X scales 39X₁ and 39X₂, respectively, and two Yheads 64 (Y encoders 70A and 70C) shown surrounded by a circle in FIG.27 facing Y scales 39Y₁ and 39Y₂, respectively, the pitching amount orrolling amount, and yawing amount of wafer stage WST measured byinterferometer system 118, the stage position induced error correctioninformation (correction information obtained by formula (22) or formula(23) previously described) of each encoder corresponding to the Zposition, the correction information of the grating pitch of each scaleand correction information of the warp of the grid line, and the Abbeoffset quantity (Abbe error correction information). Further, maincontroller 20 controls the position of wafer table WTB in the Z-axisdirection, the θy rotation (rolling), and the θx rotation (pitching),based on measurement values of one pair each of Z sensors 74 _(1,j) and74 _(2,j), and 76 _(1,q) and 76 _(2,q) that face one end and the otherend (in the embodiment, Y scales 39Y₁ and 39Y₂) of the wafer table WTBsurface in the X-axis direction. Incidentally, the position of wafertable WTB in the Z-axis direction and the θy rotation (rolling) can becontrolled based on the measurement value of Z sensors 74 _(1,j), 74_(2,j), 76 _(1,q) and 76 _(2,q), and the θx rotation (pitching) can becontrolled based on the measurement values of Y interferometer 16. Inany case, the control (focus leveling control of wafer W) of theposition of wafer table WTB in the Z-axis direction, the θy rotation,and the θx rotation during this exposure is performed, based on resultsof a focus mapping performed in advance by the multipoint AF systempreviously described.

Main controller 20 performs the exposure operation described above,based on results of wafer alignment (e.g. Enhanced Global Alignment(EGA)) that has been performed beforehand and on the latest baseline andthe like of alignment systems AL1, and AL2₁ to AL2₄, by repeating amovement operation between shots in which wafer stage WST is moved to ascanning starting position (an acceleration starting position) forexposure of each shot area on wafer W, and a scanning exposure operationin which a pattern formed on reticle R is transferred onto each shotarea by a scanning exposure method. Incidentally, the exposure operationdescribed above is performed in a state where water is retained in thespace between tip lens 191 and wafer W. Further, exposure is performedin the order from the shot area located on the −Y side to the shot arealocated on the +Y side in FIG. 27. Incidentally, details on the EGAmethod are disclosed, for example, in U.S. Pat. No. 4,780,617 and thelike.

And before the last shot area on wafer W is exposed, main controller 20controls stage drive system 124 based on the measurement value of Yinterferometer 18 while maintaining the measurement value of Xinterferometer 130 to a constant value, and moves measurement stage MST(measurement table MTB) to the position shown in FIG. 28. When themeasurement stage is moved, the edge surface of CD bar 46 (measurementtable MTB) on the −Y side touches the edge surface of wafer table WTB onthe +Y side. Incidentally, measurement table MTB and wafer table WTB canbe separated, for example, at around 300 μm in the Y-axis directionwhile monitoring, for example, the interferometer that measures theposition of each table in the Y-axis direction or the measurement valuesof the encoder so as to maintain a non-contact state (proximity state).After wafer stage WST and measurement stage MST are set to thepositional relation shown in FIG. 28 during the exposure of wafer W,both stages are moved while maintaining this positional relation.

Subsequently, as shown in FIG. 29, main controller 20 begins theoperation of driving measurement stage MST in the −Y-direction, and alsobegins the operation of driving wafer stage WST toward unloadingposition UP, while maintaining the positional relation of wafer tableWTB and measurement table MTB in the Y-axis direction. When theoperations begin, in the embodiment, measurement stage MST is moved onlyin the −Y direction, and wafer stage WST is moved in the −Y directionand the −X direction. Further, at the beginning stage of the movement,main controller 20 controls the position (including the θz rotation) ofwafer table WTB (wafer stage WST) in the XY plane, based on themeasurement values of three encoders.

When main controller 20 simultaneously drives wafer stage WST andmeasurement stage MST in the manner described above, the water (water ofliquid immersion area 14 shown in FIG. 29) which was retained in thespace between tip lens 191 of projection unit PU and wafer Wsequentially moves over wafer W→plate 28→CD bar 46→measurement tableMTB, along with the movement of wafer stage WST and measurement stageMST to the −Y side. Incidentally, during the movement above, wafer tableWTB and measurement table MTB maintain the contact state (or proximitystate) previously described. Incidentally, FIG. 29 shows a state justbefore the water of liquid immersion area 14 is moved over to CD bar 46from plate 28. Further, in the state shown in FIG. 29, main controller20 controls the position (including the θz rotation) of wafer table WTB(wafer stage WST) within the XY plane, based on the measurement values(and the stage position induced error correction information, thecorrection information of the grating pitch of the scale and thecorrection information of the grid line of encoders 70A, 70B or 70Dstored in memory 34, corresponding to the pitching amount, rollingamount, yawing amount, and the Z position of wafer stage WST measured byinterferometer system 118) of the three encoders 70A, 70B, and 70D.

When wafer stage WST and measurement stage MST are drivensimultaneously, slightly in the directions above furthermore from thestate shown in FIG. 29, respectively, because the position measurementof wafer stage WST (wafer table WTB) by Y encoder 70A (and, 70C) will nolonger be possible, main controller 20 switches the control of the Yposition and the θz rotation of wafer stage WST (wafer table WTB) justbefore this, from a control based on the measurement values of Yencoders 70A and 70C to a control based on the measurement values of Yinterferometer 16 and Z interferometers 43A and 43B. Then, after apredetermined time later, measurement stage MST reaches a position wherebaseline measurement (hereinafter appropriately referred to as Sec-BCHK(interval)) of the secondary alignment system is performed at apredetermined interval (in this case, at each wafer exchange) as shownin FIG. 30. Then, main controller 20 stops measurement stage MST at theposition, and drives wafer stage WST furthermore toward unloadingposition UP and then stops wafer stage WST at unloading position UP,while measuring the X position of wafer stage WST using X head 66 (Xlinear encoder 70B) shown in FIG. 30 surrounded by a circle that faces Xscale 39X₁ and also measuring the position in the Y-axis direction andthe θz rotation measure using Y interferometer 16 and Z interferometers43A and 43B. Incidentally, in the state shown in FIG. 30, the water isretained in the space between measurement table MTB and tip lens 191.

Subsequently, as shown in FIGS. 30 and 31, main controller 20 adjuststhe θz rotation of CD bar 46, based on the measurement values of Y-axislinear encoders 70E and 70F configured by Y heads 64 y ₁ and 64 y ₂shown in FIG. 31 surrounded by a circle that face a pair of referencegrids 52 on CD bar 46 supported by measurement stage MST, respectively,and also adjusts the XY position of CD bar 46, based on the measurementvalue of primary alignment system AL1 which detects reference mark Mlocated on or in the vicinity of center line CL of measurement tableMTB. Then, in this state, main controller 20 performs the Sec-BCHK(interval) in which the baseline (the relative position of the foursecondary alignment systems with respect to primary alignment systemAL1) of the four secondary alignment systems AL2₁ to AL2₄ is obtained bysimultaneously measuring reference mark M on CD bar 46 located withinthe field each secondary alignment system, respectively, using the foursecondary alignment systems AL2₁ to AL2₄. In parallel with this Sec-BCHK(an interval), main controller 20 gives a command to a drive system ofan unload arm (not shown) so that wafer W on wafer stage WST suspendedat unload position UP is unloaded, and also drives wafer stage WST inthe +X direction so that the stage is moved to loading position LP,while keeping a vertical movement pin CT (not shown in FIG. 30, refer toFIG. 31) elevated by a predetermined amount, which was driven upward onthe unloading.

Next, as shown in FIG. 32, main controller 20 moves measurement stageMST to an optimal waiting position (hereinafter referred to as “optimalscrum waiting position”), which is the optimal waiting position formoving measurement stage MST from the state distanced from wafer stageWST into the contact state (or proximity state) previously describedwith wafer stage WST. In parallel with this, main controller 20 gives acommand to a drive system of a load arm (not shown) so that a new waferW is loaded on wafer table WTB. In this case, because vertical movementpin CT is maintaining the state of being elevated by a predeterminedamount, wafer loading can be performed in a short period of time whencompared with the case when vertical movement pin CT is driven downwardand is housed inside the wafer holder. Incidentally, FIG. 32 shows astate where wafer W is loaded on wafer table WTB.

In the embodiment, the optimal scrum waiting position of measurementstage MST referred to above is appropriately set according to theY-coordinate of alignment marks arranged on the alignment shot area onthe wafer. Further, in the embodiment, the optimal scrum waitingposition is decided so that wafer stage WST can move into the contactstate (or proximity state) at the position where wafer stage WST stopsfor wafer alignment.

Next, main controller 20 moves wafer stage WST from loading position LP,to a position (more specifically, a position where the former process ofbase line measurement (Pri-BCHK) of the primary alignment system isperformed) in the field (detection area) of primary alignment system AL1where fiducial mark FM on measurement plate 30 shown in FIG. 33 ispositioned. On this operation, by irregular control based on themeasurement values of Encoder 70B for the X-axis direction, and Yinterferometer 16 and Z interferometer 43A and 43B for the Y-axisdirection and the θz rotation, main controller 20 controls the positionof wafer table WTB (wafer stage WST) in the XY plane. And, when waferstage WST arrives at the position shown in FIG. 33 where the formerprocess of Pri-BCHK is performed, main controller 20 switches theposition control of wafer stage WST in the XY plane from the irregularcontrol described above to the position control using the three encoders(heads) in the following procedure.

In a state where wafer stage WST has been moved to the position shown inFIG. 33 where of the former process of Pri-BCHK is performed, two Xheads 66 (of the heads, head 66 that faces X scale 39X₂ is shownsurrounded by a circle) of head unit 62D face X scales 39X₁ and 39X₂,respectively, and two Y heads 64 y ₂ and 64 y ₁, which are shown in FIG.33 surrounded by a circle, face Y scales 39Y₁ and 39Y₂, respectively. Inthis state, main controller 20 selects the two Y heads 64 y ₂ and 64 y ₁and X head 66 that faces X scale 39X₂ (these three selected heads willhereinafter be referred to as origin heads), and finely moves waferstage WST within the XY plane so that an absolute phase of each originhead will be the initial value for each origin head that has beendecided beforehand. In this case, the initial value of the absolutephase of each origin head is decided to be the measurement values of theabsolute phase of Y heads 64 y ₂ and 64 y ₁ which were obtained afteradjusting θz rotation of wafer stage WST in advance so as to make the θzrotational error of wafer stage WST become a value close to zero as muchas possible, and the measurement value of the absolute phase of theremaining origin head 66 which was measured at the same time with themeasurement values of the Y heads. Incidentally, at the point when thefine movement described above is started, the position of wafer stageWST within the XY plane is driven so that the value that the measurementvalue of each origin head decided beforehand fits within a range of onefringe of the interference fringe.

Then, at a point when the absolute phase of the three origin heads 66,64 y ₂ and 64 y ₁ each become the initial value, main controller 20begins the position control of wafer stage WST within the XY planeagain, using origin heads (Y heads) 64 y ₂ and 64 y ₁ (encoders 70A and70C) which face Y scales 39Y₁ and 39Y₂, respectively, and origin head (Xhead) 66 (encoder 70D) which face X scale 39X₂. That is, in the mannerdescribed above, main controller 20 switches the position control ofwafer stage WST in the XY plane at the position where of the formerprocess of Pri-BCHK is performed from the irregular control previouslydescribed to the position control based on the measurement values ofencoders 70A, 70C and 70D corresponding to the three origin heads 66, 64y ₂ and 64 y ₁. The position control based on the measurement values ofencoders 70A, 70C and 70D is performed by controlling the position ofwafer stage WST within the XY plane, based on the measurement values ofencoders 70A, 70C and 70D, the stage position induced error correctioninformation (the correction information that is obtained from formulas(22) and (23) previously described) of each encoder which corresponds tothe pitching amount or rolling amount, yawing amount, and the Z positionof wafer stage WST measured by interferometer system 118, the correctioninformation of the grating pitch and the correction information of thegrid line of each scale, and the Abbe offset quantity (Abbe errorcorrection information).

Subsequently, main controller 20 performs the former process of Pri-BCHKin which fiducial mark FM is detected using primary alignment systemAL1. At this point in time, measurement stage MST is waiting at theoptimal scrum waiting position described above.

Next, while controlling the position of wafer stage WST based on themeasurement values of at least the three encoders and each correctioninformation described above, main controller 20 begins the movement ofwafer stage WST in the +Y direction toward a position where thealignment marks arranged in three first alignment shot areas aredetected.

Then, when wafer stage WST reaches the position shown in FIG. 34, maincontroller 20 stops wafer stage WST. Prior to this, main controller 20activates (turns on) Z sensors 72 a to 72 d at the point when Z sensors72 a to 72 d begins to move over wafer table WTB or at the point before,and measures the Z position and the inclination (θy rotation and θxrotation) of wafer table WTB.

After wafer stage WST is stopped as in the description above, maincontroller 20 detects the alignment marks arranged in the three firstalignment shot areas substantially at the same time and alsoindividually (refer to the star-shaped marks in FIG. 34), using primaryalignment system AL1, and secondary alignment systems AL2₂ and AL2₃, andmakes a link between the detection results of the three alignmentsystems AL1, AL2₂, and AL2₃ and the measurement values (measurementvalues after the correction according to each correction information) ofat least the three encoders above at the time of the detection, andstores them in the internal memory.

As in the description above, in the embodiment, the shift to the contactstate (or proximity state) between measurement stage MST and wafer stageWST is completed at the position where detection of the alignment marksof the first alignment shot areas is performed, and from this position,main controller 20 begins to move both stages WST and MST in the +Ydirection (step movement toward the position for detecting alignmentmarks arranged in five second alignment shot areas) in the contact state(or proximity state). Prior to starting the movement of both stages WSTand MST in the +Y direction, as shown in FIG. 34, main controller 20begins irradiation of a detection beam from irradiation system 90 of themultipoint AF system (90 a, 90 b) toward wafer table WTB. Accordingly, adetection area of the multipoint AF system is formed on wafer table WTB.

Then, when both stages WST and MST reach the position shown in FIG. 35during the movement of both stages WST and MST in the +Y direction, maincontroller 20 performs the former process of the focus calibration, andobtains the relation between the measurement values (surface positioninformation on one side and the other side of wafer table WTB in theX-axis direction) of Z sensors 72 a, 72 b, 72 c, and 72 d, in a statewhere a straight line (center line) in the Y-axis direction passingthrough the center (substantially coinciding with the center of wafer W)of wafer table WTB coincides with straight line LV previously described,and the detection results (surface position information) of a detectionpoint (the detection point located in or around the center, among aplurality of detection points) on the surface of measurement plate 30 ofthe multipoint AF system (90 a, 90 b). At this point, liquid immersionarea 14 is located in the vicinity of the border of CD bar 46 and wafertable WTB. More specifically, liquid immersion area 14 is in a statejust before it is passed over to wafer table WTB from CD bar 46.

Then, when both stages WST and MST move further in the +Y direction andreach the position shown in FIG. 36 while maintaining the contact state(or proximity state), the alignment marks arranged in the five secondalignment shot areas are detected substantially at the same time andalso individually (refer to the star-shaped marks in FIG. 3), using thefive alignment systems AL1, and AL2₁ to AL2₄ and a link is made betweenthe detection results of the five alignment systems AL1, and AL2₁ toAL2₄ and the measurement values (measurement values after the correctionaccording to each correction information) of the three encoders 70A,70C, and 70D at the time of the detection, and stored in the internalmemory. At this point in time, since the X head that faces X scale 39X₁and is located on straight line LV does not exist, main controller 20controls the position within the XY plane of wafer table WTB based onthe measurement values of X head 66 facing X scale 39X₂ (X linearencoder 70D) and Y linear encoders 70A and 70C.

As is described above, in the embodiment, the positional information(two-dimensional positional information) of a total of eight alignmentmarks can be detected at the point when the detection of the alignmentmarks in the second alignment shot areas is completed. Therefore, atthis stage, main controller 20 can perform a statistical computationsuch as the one disclosed in, for example, Kokai (Japanese UnexaminedPatent Application Publication) No. 61-44429 (the corresponding U.S.Pat. No. 4,780,617) and the like, to obtain the scaling (shotmagnification) of wafer W, and can adjust the optical properties ofprojection optical system PL, such as for example, the projectionmagnification, by controlling an adjustment 68 (refer to FIG. 6) basedon the shot magnification which has been computed. Adjustment unit 68adjusts the optical properties of projection optical system PL, forexample, by driving a particular movable lens that configures projectionoptical system PL, or changing gas pressure in an airtight chamberformed between particular lenses that configure projection opticalsystem PL or the like.

Further, after the simultaneous detection of the alignment marksarranged in the five second alignment shot areas is completed, maincontroller 20 starts again movement in the +Y direction of both stagesWST and MST in the contact state (or proximity state), and at the sametime, starts the focus mapping using Z sensors 72 a to 72 d and themultipoint AF system (90 a, 90 b), as is shown in FIG. 36.

Then, when both stages WST and MST reach the position with whichmeasurement plate 30 is located directly below projection optical systemPL shown in FIG. 37, main controller 20 performs the Pri-BCHK latterprocess and the latter process of the focus calibration. In this case,the Pri-BCHK latter process refers to a processing in which a projectedimage (aerial image) of a pair of measurement marks on reticle Rprojected by projection optical system PL is measured, using aerialimage measurement unit 45 previously described which has aerial imagemeasurement slit pattern SL formed on measurement plate 30, and themeasurement results (aerial image intensity depending on the XY positionof wafer table WTB) are stored in the internal memory. In thisprocessing, the projected image of the pair of measurement marks ismeasured in an aerial image measurement operation by the slit scanmethod, using a pair of aerial image measurement slit patterns SL,respectively, similar to the method disclosed in, U.S. PatentApplication Publication No. 2002/0041377 and the like. Further, thelatter process of the focus calibration refers to a processing in whichmain controller 20 measures the aerial image of a measurement markformed on a mark plate (not shown) on reticle R or on reticle stage RSTusing aerial image measurement unit 45, while controlling the position(Z position) of measurement plate 30 (wafer table WTB) related to theoptical axis direction of projection optical system PL, based on thesurface position information of wafer table WTB (wafer stage WST)measured by Z sensors 72 a, 72 b, 72 c, and 72 d, and then measures thebest focus position of projection optical system PL based on themeasurement results, as shown in FIG. 37. For example, the measurementoperation of the projected image of the measurement mark is disclosedin, for example, the pamphlet of International Publication No. WO05/124834 and the like. While moving measurement plate 30 in the Z-axisdirection, main controller 20 takes in the measurement values of Zsensors 74 _(1,4), 74 _(2,4), 76 _(1,3), and 76 _(2,3) insynchronization with taking in the output signal from aerial imagemeasurement unit 45. Then, main controller 20 stores the values of Zsensors 74 _(1,4), 74 _(2,4), 76 _(1,3), and 76 _(2,3) corresponding tothe best focus position of projection optical system PL in a memory (notshown). Incidentally, the reason why the position (Z position) relatedto the optical axis direction of projection optical system PL ofmeasurement plate 30 (wafer stage WST) is controlled using the surfaceposition information measured in the latter process of the focuscalibration by Z sensors 72 a, 72 b, 72 c, and 72 d is because thelatter process of the focus calibration is performed during the focusmapping previously described.

In this case, because liquid immersion area 14 is formed betweenprojection optical system PL and measurement plate 30 (wafer table WTB),the measurement of the aerial image is performed via projection opticalsystem PL and water Lq. Further, because measurement plate 30 and thelike is installed in wafer stage WST (wafer table WTB), and the lightreceiving element and the like is installed in measurement stage MST,the measurement of the aerial image is performed while maintaining thecontact state (or proximity state) of wafer stage WST and measurementstage MST, as shown in FIG. 37. By the measurement described above,measurement values (more specifically, surface position information ofwafer table WTB) of Z sensors 74 _(1,4), 74 _(2,4), 76 _(1,3), and 76_(2,3) corresponding to the best focus position of projection opticalsystem PL are obtained, in a state where the straight line (the centerline) in the Y-axis direction passing through the center of wafer tableWTB coincides with straight line LV previously described.

Then, main controller 20 computes the baseline of primary alignmentsystem AL1, based on the results of the former process of Pri-BCHK andthe results of the latter process of Pri-BCHK described above. Withthis, based on the relation between the measurement values (surfaceposition information of wafer table WTB) of Z sensors 72 a, 72 b, 72 c,and 72 d obtained in the former process of the focus calibrationdescribed above and the detection results (surface position information)of the detection point on the surface of measurement plate 30 of themultipoint AF system (90 a, 90 b), and the measurement values (morespecifically, surface position information of wafer table WTB) of Zsensors 74 _(1,4), 74 _(2,4), 76 _(1,3), and 76 _(2,3) corresponding tothe best focus position of projection optical system PL which areobtained in the latter process of the focus calibration described above,main controller 20 obtains the offset at a representative detectionpoint (the detection point located in or around the center, among aplurality of detection points) of the multipoint AF system (90 a, 90 b)with respect to the best focus position of projection optical system PLand adjusts the detection origin of the multipoint AF system, forexample, by an optical method so that the offset becomes zero.

In this case, from the viewpoint of improving throughput, only oneprocessing of the latter process of Pri-BCHK described above and thelatter process of the focus calibration can be performed, or theprocedure can move on to the next processing without performing bothprocessing.

As a matter of course, in the case the latter process of Pri-BCHK is notperformed, the former process of Pri-BCHK described earlier also doesnot have to be performed, and in this case, main controller 20 only hasto move wafer stage WST from loading position LP to a position where thealignment marks arranged in the first alignment shot areas are detected.Incidentally, in the case Pri-BCHK processing is not performed, thebaseline which is measured by a similar operation just before theexposure of a wafer exposed earlier than wafer W subject to exposure isused. Further, when latter process of the focus calibration is notperformed, similar to the baseline, the best focus position ofprojection optical system PL which is measured just before the exposureof a preceding wafer is used.

Incidentally, in the state shown in FIG. 37, the focus mappingpreviously described is being continued.

When wafer stage WST reaches the position shown in FIG. 38 by movementin the +Y direction of both stages WST and MST in the contact state (orproximity state) described above, main controller 20 stops wafer stageWST at that position, while also making measurement stage MST continuethe movement in the +Y direction. Then, main controller 20 almostsimultaneously and individually detects the alignment marks arranged inthe five third alignment shot areas AS (refer to star-shaped marks inFIG. 38) using five alignment systems AL1 and AL2₁ to AL2₄, links thedetection results of five alignment systems AL1 and AL2₁ and AL2₄ andthe measurement values of the four encoders at the time of the detectionand stores them in the internal memory. At this point in time, the focusmapping is being continued.

Meanwhile, after a predetermined period of time from the suspension ofwafer stage WST described above, measurement stage MST and wafer stageWST moves from the contact state (or proximity state) into a separationstate. After moving into the separation state, main controller 20 stopsthe movement of measurement stage MST when measurement stage MST reachesan exposure start waiting position where measurement stage MST waitsuntil exposure is started.

Next, main controller 20 starts to move wafer stage WST in the +Ydirection toward a position where alignment marks arranged in threefourth alignment shot areas are detected. At this point in time, thefocus mapping is being continued. Meanwhile, measurement stage WST iswaiting at the exposure start waiting position described above.

Then, when wafer stage WST reaches the position shown in FIG. 39, maincontroller 20 immediately stops wafer stage WST, and almostsimultaneously and individually detects the alignment marks arranged inthe three fourth alignment shot areas on wafer W (refer to star-shapedmarks in FIG. 39) using primary alignment system AL1 and secondaryalignment systems AL2₂ and AL2₃, links the detection results of threealignment systems AL1, AL2₂ and AL2₃ and the measurement values of thefour encoders at the time of the detection, and stores them in theinternal memory. Also at this point in time, the focus mapping is beingcontinued, and measurement stage MST is still waiting at the exposurestart waiting position. Then, using the detection results of a total of16 alignment marks and the measurement values (measurement values afterthe correction by each correction information) of the correspondingencoders obtained in the manner described above, main controller 20computes array information (coordinate values) of all the shot areas onwafer W on a coordinate system (for example, an XY coordinate systemwhose origin is placed at the center of wafer table WTB) that is set bythe measurement axes of the four encoders, using the EGA methoddisclosed in, for example, U.S. Pat. No. 4,780,617 and the like.

Next, main controller 20 continues the focus mapping while moving waferstage WST in the +Y direction again. Then, when the detection beam fromthe multipoint AF system (90 a, 90 b) moves off the wafer W surface, asis shown in FIG. 40, main controller 20 ends the focus mapping. Afterthat, based on the results of the wafer alignment (EGA) describedearlier performed in advance, the latest baselines of the five alignmentsystems AL1 and AL2₁ to AL2₄, and the like, main controller 20 performsexposure by the step-and-scan method in a liquid immersion exposure andsequentially transfers a reticle pattern to a plurality of shot areas onwafer W. Afterwards, similar operations are repeatedly performed so asto expose the remaining wafers within the lot.

As discussed in detail above, according to exposure apparatus 100related to the embodiment, the positional information (including the θzrotation) of wafer stage WST within the XY plane is measured by threeencoders, which at least include one each of an X encoder and a Yencoder of the encoder system, while wafer stage WST is being driven.Then, main controller 20 switches an encoder (a head) used for measuringthe positional information of wafer stage WST in the XY plane from oneof the encoders of the three encoders to another encoder, so that theposition of wafer stage WST within the XY plane is maintained before andafter the switching. Because of this, although the encoder which is usedfor the control of the position of wafer stage WST has been switched,the position of wafer stage WST within the XY plane is maintained beforeand after the switching, which makes an accurate linkage possible.Further, also on the switching of the encoder, main controller 20 usesthe measurement values of each encoder whose measurement errors of thehead (encoder) due to the measurement delay previously described havebeen corrected. Accordingly, it becomes possible to move wafer stage WSTtwo-dimensionally, precisely along a predetermined course, whileperforming linkage between a plurality of encoders.

Further, according to exposure apparatus 100 related to the embodiment,for example, while the lot is being processed, main controller 20measures the positional information (including the θz rotation) of waferstage WST within the XY plane (the movement plane) by three heads(encoders), which at least include one each of an X head (X encoder) anda Y head (Y encoder) of the encoder system. Then, based on themeasurement results of the positional information and the positionalinformation ((X, Y) coordinate value) in the movement plane of the threeheads used for measuring the positional information, main controller 20drives wafer stage WST within the XY plane. In this case, maincontroller 20 drives wafer stage WST within the XY plane, whilecomputing the positional information of wafer stage WST within the XYplane using the affine transformation relation. Accordingly, it becomespossible to control the movement of wafer stage WST with good precisionwhile switching the head (encoder) used for control during the movementof wafer stage WST, using the encoder system including head units 62A to62D which respectively have a plurality of Y heads 64 or a plurality ofX heads 66.

Further, according to exposure apparatus 100 of the embodiment, whilewafer stage WST is being driven, main controller 20 takes in the outputof each encoder (a head) of the encoder system constantly (at apredetermined measurement sampling interval), as well as executes anoperation where the encoder used for position control of wafer stage WSTis switched from an encoder (a head) that has been used for positioncontrol of wafer stage WST to another encoder (a head) insynchronization with the timing of the position control of wafer stageWST. Therefore, the switching of the encoder no longer has to beperformed at a high speed in synchronization with the measurementsampling where the output of the interferometer and the encoder is takenin, and a highly precise hardware for the switching will not benecessary, which consequently will make cost reduction possible.

Further, according to exposure apparatus 100 of the embodiment, maincontroller 20 can make out a combination of encoders subject to theswitching of the encoder used for position control of wafer stage WSTfrom an arbitrary encoder of the encoder system to another encoder andprepare a schedule in advance for the timing of the switching, based onthe movement course of wafer stage WST. Then, during the movement ofwafer stage WST, main controller 20 measures the positional informationof wafer stage WST within the XY plane using the three encoders of theencoder system, and based on the contents above that have beenscheduled, the switching from the arbitrary encoder to the anotherencoder is performed. According to this, a reasonable encoder switchingaccording to the target track of wafer stage WST becomes possible.

Further, according to exposure apparatus 100 of the embodiment, in thecase of moving wafer stage WST in a predetermined direction, such as,for example, the Y-axis direction at the time of wafer alignment time orexposure, wafer stage WST is driven in the Y-axis direction, based onthe measurement information of the encoder system, the positionalinformation (including inclination information, e.g., rotationinformation in the θx direction) of wafer stage WST in a directiondifferent from the Y-axis direction, the characteristic information(e.g., the degree of flatness of the grating surface, and/or a gratingformation error) of the scale, and the correction information of theAbbe error due to the Abbe offset quantity of the scale. Morespecifically, wafer stage WST is driven to compensate for themeasurement errors of the encoder system (encoders 70A and 70C) causedby the displacement (including the inclination) of wafer stage WST in adirection different from the Y-axis direction and the scale. In theembodiment, main controller 20 drives wafer stage WST in the Y-axisdirection, based on the measurement values of encoders 70A and 70C whichmeasure the positional information of wafer stage WST in a predetermineddirection, such as, for example, in the Y-axis direction, the positionalinformation of wafer stage WST in a direction different from the Y-axisdirection at the time of the measurement (direction besides themeasurement direction), such as, for example, the stage position inducederror correction information (the correction information which iscomputed by formula (22) previously described) that corresponds to thepositional information of wafer stage WST in the θx direction, θzdirection, and the Z-axis direction measured by Y interferometer 16 andZ interferometers 43A and 43B of interferometer system 118, thecorrection information (the correction information which takes intoconsideration the unevenness (degree of flatness) of the Y scale) of thegrating pitch of the Y scale, the correction information of the warp ofgrid line 38 of the Y scale, and the correction information of the Abbeerror due to the Abbe offset quantity of the Y scale. In the mannerdescribed above, stage drive system 124 is controlled and wafer stageWST is driven in the Y-axis direction, based on the measurement valuesof encoders 70A and 70C which are corrected according to each correctioninformation of the relative displacement of scales 39Y₁ and 39Y₂ and Yhead 64 in the direction besides the measurement direction, themeasurement errors of encoders 70A and 70C, due to the grating pitch ofY scales 39Y₁ and 39Y₂ the warp of grid line 38, and the Abbe error dueto the Abbe offset quantity of the Y scale. In this case, themeasurement values (count values) of encoders 70A and 70C are the sameresults as when an ideal grating (diffraction grating) is measured withan ideal encoder (head). An ideal grating (diffraction grating), here,refers to a grating whose surface of the grating is parallel to themovement plane (the XY plane) of the stage and is a completely flatsurface, and the pitch direction of the grating is parallel to the beamof the interferometer and the distance between the grid lines iscompletely equal. An ideal encoder (head) refers to a head whose opticalaxis is perpendicular to the movement plane of the stage and whosemeasurement values do not change by Z displacement, leveling, yawing andthe like.

Further, in the case wafer stage WST is moved in the X-axis direction,wafer stage WST is driven in the X-axis direction, based on themeasurement information of the encoder system, the positionalinformation (including inclination information, e.g., rotationinformation in the θy direction) of wafer stage WST in a directiondifferent from the X-axis direction, the characteristic information(e.g., the degree of flatness of the grating surface, and/or a gratingformation error) of the scale, and the correction information of theAbbe error due to the Abbe offset quantity of the scale. Morespecifically, wafer stage WST is driven to compensate for themeasurement errors of the encoder system (encoders 70B and 70D) causedby the displacement (including the inclination) of wafer stage WST in adirection different from the X-axis direction. In the embodiment, maincontroller 20 drives wafer stage WST in the X-axis direction, based onthe measurement values of encoders 70B and 70D which measure thepositional information of wafer stage WST in the X-axis direction, thepositional information of wafer stage WST in a direction different fromthe X-axis direction at the time of the measurement (direction besidesthe measurement direction), such as, for example, the stage positioninduced error correction information (the correction information whichis computed by formula (23) previously described) that corresponds tothe positional information of wafer stage WST in the θy direction, θzdirection, and the Z-axis direction measured by Z interferometers 43Aand 43B of interferometer system 118, the correction information (thecorrection information which takes into consideration the unevenness(degree of flatness) of the X scales) of the grating pitch of the Xscales, the correction information of the warp of grid line 37 of the Xscales, and the correction information of the Abbe error due to the Abbeoffset quantity of X scales 39X₁ and 39X₂. In the manner describedabove, stage drive system 124 is controlled and wafer stage WST isdriven in the X-axis direction, based on the measurement values ofencoders 70B and 70D which are corrected according to each correctioninformation of the relative displacement of X scales 39X₁ and 39X₂ and Xhead 66 in the direction besides the measurement direction, themeasurement errors of encoders 70B and 70D, due to the grating pitch ofX scales 39X₁ and 39X₂ the warp of grid line 37, and the Abbe error dueto the Abbe offset quantity of X scales 39X₁ and 39X₂. In this case, themeasurement values of encoders 70B and 70D are the same results as whenan ideal grating (diffraction grating) is measured with an ideal encoder(head).

Accordingly, it becomes possible to drive wafer stage WST using anencoder in a desired direction with good precision, without beingaffected by the relative motion in directions other than the direction(measurement direction) of the head and the scale to be measured,without being affected by the Abbe error, without being affected by theunevenness of the scale, and without being affected by the grating pitchof the scale and the grating warp.

Further, according to exposure apparatus 100 of the embodiment, when thepattern of reticle R is formed in each shot area on the wafer, exposureby the step-and-scan method is performed, and during the exposureoperation of this step-and-scan method, main controller 20 performs thelinkage operation between the plurality of encoders, between theencoders (between combinations of the encoders) in accordance with theschedule set in advance, at a timing in accordance with the schedule, insynchronization with the timing of the position control of wafer stageWST.

Further, according to exposure apparatus 100 related to the embodiment,when wafer stage WST is driven in a predetermined direction within theXY plane by main controller 20, the measurement data corresponding tothe detection signals of a total of three heads including at least oneof the encoder systems, such as, for example, an X head and a Y head, istaken in at a predetermined control sampling interval (for example, 96[μsec]), respectively, and based on the measurement data which was takenin the latest and the data just before the latest data (one controlsampling interval earlier) for each head, and the information of delaytime δ that accompanies the detection signals propagating through thecable (propagation path), wafer stage WST is driven so that themeasurement errors of the head (encoder) due to the measurement delaythat accompanies the detection signals propagating though the cable(propagation path) are corrected. According to this, it becomes possibleto drive wafer stage WST with high precision in the desired directionwithout being affected by the measurement delay that accompanies thedetection signals of the head of the encoder propagating through thecable (propagation path).

For example, in exposure apparatus 100 of the embodiment, in the casewafer stage WST is driven in the Y-axis, the positional information ofwafer stage WST is measured using a total of three heads (encoders) thatinclude encoders 70A and 70C each having a pair of Y heads 64 whichfaces Y scales 39Y₁ and 39Y₂, respectively. On this measurement, even ifdelay time δ between the pair of Y heads 64 that each faces Y scales39Y₁ and 39Y₂ is different, because main controller drives wafer stageWST so that the measurement errors of the head (encoder) due to delaytime δ are corrected, there consequently is no risk of the θz rotationalerror occurring in wafer stage WST according to the difference in delaytime δ described above between the pair of Y heads 64.

Further, in the embodiment, prior to the drive of wafer stage WSTdescribed above, for example, such as at the startup time of theapparatus, main controller 20 drives wafer stage WST in a predetermineddirection (e.g. the Y-axis direction (or the X-axis direction)) withinthe XY plane, and during the drive, for a plurality of Y heads 64 (or Xheads 66) of the encoder system, such as for example, a pair, takes inthe detection signals of each head and detection signals of Yinterferometer 16 (or X interferometer 126) of interferometer system 118in memory 34 simultaneously at a predetermined sampling timing, andbased on both of the detection signals, executes a delay timeacquisition process of acquiring information of the delay time for eachhead the with the detection signals of the corresponding interferometerserving as a reference. In the manner described above, it becomespossible for exposure apparatus 100 (main controller 20) itself toacquire the information of the delay time of the detection signals ofeach of the plurality of heads with the detection signals of thecorresponding interferometer of interferometer system 118 serving as areference.

Then, based on the information of the delay time for each of theplurality of heads of the encoder system that has been acquired, and themeasurement data corresponding to the detection signals of each of theplurality of heads, main controller 20 drives wafer stage WST in themanner described above. Accordingly, even if the delay time is differentfor each head, it becomes possible to drive wafer stage WST using eachencoder of the encoder system with good precision, without beingaffected by the difference of the delay time between the plurality ofheads.

Further, according to exposure apparatus 100 of the embodiment, whenmain controller 20 completes the exposure of wafer W on wafer stage WST,wafer stage WST is sequentially moved to unloading position UP and thento loading position LP, and unloading of wafer W that has been exposedfrom wafer stage WST and loading of a new wafer W on wafer stage WST, ormore specifically, exchange of wafer W is performed on wafer stage WST.Each time the exchange of wafer W is completed, main controller 20 setsthe position of wafer stage WST at the processing position where theformer process of Pri-BCHK described earlier is performed, and startsthe position control of wafer stage WST within the XY plane using thethree encoders of the encoder system once more, according to theprocedure previously described. Therefore, even if the linkage process(the switching process of the encoder used for the position control ofwafer stage WST in the XY plane) between the plurality of encoderspreviously described is repeatedly performed, the position error (thecumulative error which is accumulated each time the linkage process isperformed) of wafer stage WST that accompanies the linkage process iscanceled each time exchange of wafer W is performed, so the positionerror of wafer stage WST never accumulates beyond a permissible level.Accordingly, the encoder system makes it possible to measure thepositional information of wafer stage WST within the XY plane in theeffective area previously described that includes the exposure positionwith good precision for over a long period, which in turn makes itpossible to maintain the exposure precision for over a long period oftime.

Further, in the embodiment, main controller 20 starts the positioncontrol of wafer stage WST within the XY plane using the three encodersof the encoder system once more, in a state in which yawing of waferstage WST is adjusted to a position where the absolute phase of a pairof origin heads 64 y ₂ and 64 y ₁ which are spaced apart by distance L(≧400 mm) becomes the initial value that has been decided in advance.Because of this, the yawing error of wafer stage WST based on themeasurement values of three origin heads at the control starting pointwithin the XY plane of wafer stage WST can be set approximately to 0,and as a result, the shift of the baseline of the primary alignmentsystem in the X-axis direction that accompanies the yawing error ofwafer stage WST, chip rotation (rotational error of the shot area onwafer W), and the generation of overlay error that accompanies the chiprotation can be effectively controlled.

Further, in the embodiment, each time exchange of wafer W is performedon wafer stage WST, prior to starting the EGA alignment measurement, orto be more specific, prior to the measurement of the alignment marksarranged in the three first alignment shot areas on wafer W by alignmentsystems AL1, AL2₂, and AL2₃, main controller 20 begins the positioncontrol of wafer stage WST within the XY plane using the three encodersonce more. Therefore, even if there are some errors in the measurementvalues of the X position and the Y position of wafer stage WST measuredby the encoder at the point in time when position control of wafer stageWST within the XY plane using the three encoders is started once more,the errors are consequently canceled by the EGA performed next.

Further, in the embodiment, as shown in FIGS. 30, 31, and 32, maincontroller 20 continues the measurement of the positional information ofwafer stage WST in the X-axis direction, which is the measurementdirection of X encoder 70B, even while exchange of wafer W is beingperformed on wafer stage WST, using X encoder 70B (X head 66, which is ahead of head unit 62D that faces X scale 39X₂) of the encoder system.Therefore, X interferometer 128, which measures the X position of waferstage WST in the vicinity of unloading position UP and loading positionLP, does not necessarily have to be arranged. However, in theembodiment, X interferometer 128 is arranged for the purpose of backup,such as at the time of abnormality of the encoder.

Further, according to exposure apparatus 100 of the embodiment, forrelative movement between illumination light IL irradiated on wafer Wvia reticle R, projection optical system PL, and water Lq fromillumination system 10 and wafer W, main controller 20 drives waferstage WST on which wafer W is placed with good precision, based on themeasurement values of each encoder described above, the stage positioninduced error correction information of each encoder corresponding tothe positional information of the wafer stage in the direction besidesthe measurement direction at the time of the measurement, the correctioninformation of the grating pitch of each scale and the correctioninformation of the grid line, and the correction information of the Abbeerror due to the Abbe offset quantity of each scale.

Accordingly, by scanning exposure and liquid immersion exposure, itbecomes possible to form a desired pattern of reticle R in each shotarea on the wafer with good precision.

Further, in the embodiment, as it has been described earlier based onFIGS. 33 and 34, prior to the measurement (EGA alignment measurement) ofthe alignment marks arranged in the three first alignment shot areas onwafer W by alignment systems AL1, AL2₂, and AL2₃, main controller 20switches the measurement unit used for the position control of waferstage WST from interferometer system 118 to the encoder system (switchesthe control of the position of wafer table WTB within the XY plane fromthe irregular control previously described to the control based on themeasurement values of at least three encoders out of encoders 70B and70D and encoders 70A and 70C). According to this, even if there are someerrors in the measurement values of the X position and the Y position ofwafer stage WST by the encoder system just after the switching, there isan advantage of the errors being consequently canceled by the EGAperformed next.

Further, according to the embodiment, on acquiring the stage positioninduced error correction information of the measurement values of theencoder previously described, main controller 20 changes wafer stage WSTinto a plurality of different attitudes, and for each attitude, in astate where the attitude of wafer stage WST is maintained based on themeasurement results of interferometer system 118, moves wafer stage WSTin the Z-axis direction in a predetermined stroke range whileirradiating a detection light from head 64 or 66 of the encoder on thespecific area of scales 39Y₁, 39Y₂, 39X₁or 39X₂, and samples themeasurement results of the encoder during the movement. According tothis, change information (for example, an error characteristics curve asshown in the graph in FIG. 12) of the measurement values of the encodercorresponding to the position in the direction (Z-axis direction)orthogonal to the movement plane of wafer stage WST for each attitudecan be obtained.

Then, by performing a predetermined operation based on this samplingresult, namely the change information of the measurement values of theencoder corresponding to the position of wafer stage WST in the Z-axisdirection for each attitude, main controller 20 obtains the correctioninformation of the measurement values of the encoder corresponding tothe positional information of wafer stage WST in the direction besidesthe measurement direction. Accordingly, the stage position induced errorcorrection information for correcting the measurement errors of theencoder due to a relative change between the head and the scale in thedirection besides the measurement direction can be determined by asimple method.

Further, in the embodiment, in the case of deciding the correctioninformation above, for a plurality of heads that configure the same headunit, such as, for example, a plurality of Y heads 64 that configurehead unit 62A, because a detection light is irradiated from each Y head64 on the same specific area of the corresponding Y scale 39Y₁, thesampling described above is performed on the measurement results of theencoder, and the stage position induced error correction information ofeach encoder configured by each Y head 64 and Y scale 39Y₁ is determinedbased on the sampling result, by using this correction information, ageometric error which occurs because of the gradient of the head is alsoconsequently corrected. In other words, when main controller 20 obtainsby the correction information with the plurality of encoderscorresponding to the same scale as the object, it obtains the correctioninformation of the encoder serving as the object taking intoconsideration the geometric error which occurs by the gradient of thehead of the object encoder when wafer stage WST is moved in the Z-axisdirection. Accordingly, in the embodiment, a cosine error caused bydifferent gradient angles in a plurality of heads is also not generated.Further, even if a gradient does not occur in Y head 64, for example,when a measurement error occurs in an encoder caused by the opticalproperties (telecentricity) of the head or the like, obtaining thecorrection information similarly can prevent the measurement error fromoccurring, which in turn prevents the deterioration of the positioncontrol precision of wafer stage WST. That is, in the embodiment, waferstage WST is driven so as to compensate for the measurement errors(hereinafter also referred to as a head induced error) of the encodersystem which occur due to the head unit. Incidentally, for example,correction information of the measurement values of the encoder systemcan be computed, based on the characteristic information (for example,including the gradient of the head and/or the optical properties and thelike) of the head unit.

Incidentally, in the embodiment above, on the switching of the encoderused for position control of wafer stage WST, the case has beendescribed where of the three encoders (head) that measure the positionalinformation of wafer stage WST within the movement plane in directionsof three degrees of freedom, one encoder (head) was switched to anotherencoder (head) so that the position (X, Y, θz) of wafer stage WST withinthe XY plane (movement plane) in directions of three degrees of freedomis maintained before and after the switching, however, the presentinvention is not limited to this. For example, in the case when amovable body is not allowed to rotate within the movement plane, thedegree of freedom that the movable body has is only two degrees offreedom (X, Y) in the movement plane, however, the present invention canbe applied even to such a case. More specifically, in this case, anencoder system that includes a total of three or more encoders includingat least one each of a first encoder which measures positionalinformation of the movable body in a direction that is parallel to afirst axis within the movement plane and a second encoder which measurespositional information of the movable body in a direction parallel to asecond axis orthogonal to the first axis in the movement plane can beused by a controller, and the controller can switch an encoder used formeasurement of the positional information of the movable body within themovement plane from an encoder of either of at least two encoders thatinclude each one of the first encoder and the second encoder to anotherencoder, so as to maintain the position of the movable body within themovement plane before and after the switching. In the case of such anarrangement, the position of the movable body within the movement planebefore and after the switching is maintained although the switching ofthe encoder used for controlling the position of the movable body isperformed, which allows a precise linkage to be performed, which in turnmakes it possible to perform linkage between a plurality of encoderswhile moving the movable body two-dimensionally precisely along apredetermined course. Further, similar to the embodiment above, thecontroller can make out a combination of the encoders subject to theswitching and prepare the schedule for the switching timing based on themovement course of the movable body, as well as constantly takes in themeasurement values of each encoder of the encoder system, and thecontroller can also execute an operation to switch the encoder used forcontrol of the movable body from an encoder of either of at least thetwo encoders used for position control of the movable body to anotherencoder in synchronization with the timing of the position control ofthe movable body.

Further, on the switching described above, the controller can computethe positional information of the movement plane of the movable body bya computing formula using the affine transformation relation based onthe measurement value of at least the two encoders used for positioncontrol of the movable body before the switching, and can decide theinitial value of the measurement value of the another encoder so as tosatisfy the computed results.

Incidentally, in the embodiment above, a movable body drive system wasdescribed in which an encoder system including an a plurality ofencoders which measure the positional information of a wafer stage thatmoves within a two-dimensional plane is equipped, and main controller 20constantly takes in the output of each encoder of the encoder system andexecutes an operation of switching an encoder used for position controlof the movable body from an encoder that has been used for positioncontrol of the movable body to another encoder, at a timing insynchronization with the position control of the movable body, however,besides such a system, for example, in a movable body drive systemequipped with the encoder system including a plurality of encoders whichmeasure the positional information of a movable body that moves only ina one-dimensional direction, the controller can constantly take in theoutput of each encoder of the encoder system and execute an operation ofswitching an encoder used for position control of the movable body froman encoder that has been used for position control of the movable bodyto another encoder, at a timing in synchronization with the positioncontrol of the movable body. Even in such a case, the switching of theencoder will not have to be performed at a high speed, and a highlyprecise hardware for the switching will not be necessary, whichconsequently will make cost reduction possible.

Further, in the embodiment above, the case has been described where maincontroller 20 makes out a combination of the encoders subject to theswitching of the encoder from an arbitrary encoder out of the threeencoders of the encoder system that measures the positional informationof wafer stage WST in directions of three degrees of freedom within themovement plane (XY plane) to another encoder and prepares the schedulefor the switching timing based on the movement course of the movablebody, however, the present invention is not limited to this. Forexample, there are movable bodies in which the movement of the movablebody is allowed only in directions of two degrees of freedom or in adirection of one degree of freedom, however, even in a movable bodydrive system that drives such a movable body within the movement plane,if the system is equipped with an encoder system including a pluralityof encoders for measuring the positional information of the movable bodywithin the movement plane, it is desirable to make out a combination ofthe encoders subject to the switching of the encoder from an arbitraryencoder of the encoder system used for position control of the movablebody to another encoder and prepare the schedule for the switchingtiming based on the movement course of the movable body, similar to theembodiment described above. According to this, a reasonable encoderswitching according to the target track of the movable body becomespossible. Further, in this case as well, the controller can constantlytake in the output of each encoder of the encoder system and execute anoperation of switching an encoder used for position control of themovable body from an encoder that has been used for position control ofthe movable body to another encoder, at a timing in synchronization withthe position control of the movable body.

When wafer stage WST is moved in the X-axis direction, in the embodimentabove, for example, the switching of the head and linkage process ofhead unit 62A and head unit 62C is performed simultaneously, or a partof the process is performed in parallel, however, the process can beperformed in head units 62A and 62C at a different timing. In this case,for example, the distance between adjacent heads is to be the same inhead units 62A and 62C, and the position of head units 62A and 62Cplaced in the X-axis direction can be shifted.

Incidentally, in the embodiment above, an invention related to theswitching of the head of the encoder and the linkage of the measurementvalue, an invention related to the correction of various measurementerrors (e.g., stage position induced error, head induced error, scaleinduced error, Abbe error and the like) of the encoder system, aninvention (invention about the reset of the encoder system) in which theposition control of the wafer stage using the encoder system was startedonce more after every wafer exchange, an invention related to theswitching timing in which the switching operation of the encoder (head)is executed at a timing in synchronization with the position control ofthe wafer stage, an invention to prepare the schedule for the switchingtiming based on the movement course of the wafer stage, an inventionassociated with the correction of the measurement errors of the encoderhead due to the measurement delay that accompanies the propagation ofthe detection signal and the like were carried out by the same exposureapparatus. However, the inventions above can be executed alone or in anycombination.

Further, in combination with the head switching/the linkage processpreviously described, a correction of the stage position induced error,the head induced error, the scale induced error and the Abbe errorpreviously described or a combination of two or more of the correctionscan also be performed.

Incidentally, in the embodiment above, the case has been described wheremain controller 20 computes an approximation straight line (for example,refer to straight line y=y_(cal)(t) shown in FIG. 10) with respect tothe temporal change (for example, refer to temporal change curve y=y(t)shown in FIG. 10) of the position of wafer stage WST, based on thelatest measurement values of each encoder (head) acquired at currenttime t and the measurement values of each encoder just before the latestmeasurement value (one control sampling interval), and drives waferstage WST using the approximation straight line so that the measurementerrors due to the measurement delay that accompanies the propagation ofthe detection signal of each head of the encoder system through thepropagation path are corrected, however, the present invention is notlimited to this. More specifically, in the present invention, inaddition to the latest measurement data and the measurement data justbefore the latest measurement data (one control sampling interval), thecontroller can compute a secondary approximate curve of the temporalchange curve of the position of the movable body using measurement datatwo measurements before the latest measurement data (two controlsampling interval), and can drive wafer stage WST so that themeasurement errors due to the measurement delay that accompanies thepropagation of the detection signal of each head of the encoder systemthrough the propagation path are corrected based on the approximationcurve. The important thing is the controller should drive the movablebody based on a plurality of data which includes the latest measurementdata of the head of the encoder system and previous data including atleast the measurement data just before the latest measurement data andon information of the delay time that accompanies the propagation thedetection signal of the head through the cable, so that the measurementerrors due to the measurement delay of the head are corrected.

Further, in the embodiment above, based on the detection signals of eachY head (each or, X head) of the encoder system and the detection signalsof Y interferometer 16 (or X interferometer 126), main controller 20performed the delay time acquisition process in which the information ofthe delay time of each Y head (or each X head) was acquired with thedetection signals of Y interferometer 16 (or X interferometer 126)serving as a reference, however, the present invention is not limited tothis, and by obtaining the difference of the delay time that accompaniesthe propagation of the detection signal of one of the X heads (or Yheads) through the cable and the delay time that accompanies thepropagation of the detection signal of other X heads (or Y heads),information of the delay time for other X heads (or Y head) can beacquired with the detection signals of the one X head (or Y head) aboveserving as a reference.

Further, in the embodiment above, main controller 20 performed the delaytime acquisition process on all heads of the encoder system, however,the present invention is not limited to this, and the delay timeacquisition process can be performed on some heads.

Further, in the embodiment above, as it has been described referring toFIG. 20, on the delay time acquisition process, main controller 20obtained the information of the delay time based on intensity differenceΔI of each head, e.g. detection signal C2 of Y head 64 and thecorresponding interferometer, e.g. output signal C1 of Y interferometer16, and computed the information of delay time δ above for Y head 64,however, the present invention is not limited to this, and theinformation of the delay time can be obtained directly, from the shiftof both signals in the temporal axis direction.

Incidentally, in the embodiment above, the case has been described whereall heads of head unit 62D except for one head 66 no longer face thescale at the unloading position and the loading position, and theposition measurement of the wafer stage within the XY plane by theencoder system could no longer be performed physically, however, thepresent invention is not limited to this. More specifically, even if theposition measurement of the wafer stage within the XY plane by theencoder system can be continued even at the unloading position and theloading position, it is desirable to begin the position measurement andposition control of wafer stage WST using the three encoders once more,at any point while wafer stage WST returns from the wafer exchangeposition to the alignment area, similar to the embodiment above. Bydoing so, the cumulative error of the wafer stage position thataccompanies the linkage process repeatedly performed between a pluralityof encoders can be canceled regularly.

Incidentally, in the embodiment above, in order to simplify thedescription, main controller 20 had control over each part of theexposure apparatus such as the stage system, the interferometer system,the encoder system and the like, however, the present invention is notlimited to this, and it is a matter of course that at least a part ofthe control performed by main controller 20 can be shared with aplurality of controllers. For example, a stage controller, whichcontrols wafer stage WST based on the measurement values of the encodersystem, the Z sensor and the interferometer system, can be arranged tooperate under main controller 20. Further, the control that maincontroller 20 performs does not necessarily have to be realized byhardware, and the control can be realized by software using a computerprogram that sets the operation of main controller 20 or each operationof some controllers that share the control as previously described.

Incidentally, the configuration and the placement of the encoder system,the interferometer system, the multipoint AF system, the Z sensor andthe like in the embodiment above is an example among many, and it is amatter of course that the present invention is not limited to this. Forexample, in the embodiment above, an example was indicated of a casewhere the pair of Y scales 39Y₁ and 39Y₂ used for the measurement of theposition in the Y-axis direction and the pair of X scales 39X₁ and 39X₂used for the measurement of the position in the X-axis direction arearranged on wafer table WTB, and corresponding to the scales, the pairof head units 62A and 62C is placed on one side and the other side ofthe X-axis direction of projection optical system PL, and the pair ofhead units 62B and 62D is placed on one side and the other side of theY-axis direction of projection optical system PL. However, the presentinvention is not limited to this, and of Y scales 39Y₁ and 39Y₂ used forthe measurement of the position in the Y-axis direction and X scales39X₁ and 39X₂ used for the measurement of the position in the X-axisdirection, at least one of the scales can be arranged singularly onwafer table WTB, without being a pair, or, of the pair of head units 62Aand 62C and the pair of head units 62B and 62D, at least one of the headunits can be arranged, singularly. Further, the extension direction ofthe scale and the extension direction of the head unit are not limitedto an orthogonal direction such as the X-axis direction and the Y-axisdirection in the embodiment above, and it can be any direction as longas the directions intersect each other. Further, the periodic directionof the diffraction grating can be a direction orthogonal to (orintersecting with) the longitudinal direction of each scale, and in sucha case, a plurality of heads of the corresponding head unit should beplaced in a direction orthogonal to the periodic direction of thediffraction grating. Further, each head unit can have a plurality ofheads placed without any gap in a direction orthogonal to the periodicdirection of the diffraction grating.

Further, in the embodiment above, the case has been described where theX scale and the Y scale were placed on a surface parallel to the XYplane of wafer stage WST, or to be more concrete, on the upper surface,however, the present invention is not limited to this, and the gratingcan be placed, as a matter of course, on the lower surface, or on theside surface of wafer stage WST. Or an encoder system having aconfiguration in which a head is arranged on a wafer stage, and atwo-dimensional grating (or a one-dimensional grating section which isarranged two-dimensionally) placed external to the movable body can beemployed. In this case, when a Z sensor is placed on the wafer stageupper surface, the two-dimensional grating (or the one-dimensionalgrating section which is arranged two-dimensionally) can also be used asa reflection surface reflecting the measurement beam from a Z sensor.

Incidentally, in the embodiment above, rotation information (pitchingamount) of wafer stage WST in the θx direction was measured byinterferometer system 118, however, for example, the pitching amount canbe obtained from the measurement values of either of the pair of Zsensors 74 _(1,j) or 76 _(p,q). Or, similar to head units 62A and 62C,for example, one Z sensor or a pair of Z sensors can be arranged inproximity each head of head units 62B and 62D, and the pitching amountcan be obtained from X scales 39X₁ and 39X₂ and the measurement value ofthe Z sensors that face the scales, respectively. Accordingly, itbecomes possible to measure the positional information of wafer stageWST in directions of six degrees of freedom, or more specifically, theX-axis, Y-axis, Z-axis, θx, θy, and θz directions using the encoder andthe Z sensor previously described, without using interferometer system118. The measurement of the positional information of wafer stage WST indirections of six degrees of freedom using the encoder and the Z sensorpreviously described can be performed not only in the exposure operationbut also in the alignment operation and/or the focus mapping operationpreviously described.

Further, in the embodiment above, the measurement values of the encodersystem were corrected based on the correction information previouslydescribed so as to compensate for the measurement errors of the encodersystem that occur due to displacement (relative displacement of the headand the scale) of wafer stage WST in a direction different from apredetermined direction in which wafer stage WST is driven, however, thepresent invention is not limited to this, and the target position forsetting the position of wafer stage WST based on the correctioninformation previously described can be corrected, for example, whiledriving wafer stage WST based on the measurement values of the encodersystem. Or, especially in the exposure operation, the position ofreticle stage RST can be corrected based on the correction informationpreviously described, while, for example, driving wafer stage WST basedon the measurement values of the encoder system.

Further, in the embodiment above, wafer stage WST was driven based onthe measurement value of the encoder system, for example, in the case ofexposure, however, for example, an encoder system the measures theposition of reticle stage RST can be added, and reticle stage RST can bedriven based on the correction information that corresponds to themeasurement values of the encoder system and the positional informationof the reticle stage in the direction besides the measurement directionmeasured by reticle interferometer 116.

Further, in the embodiment above, the case has been described where theapparatus is equipped with one fixed primary alignment system and fourmovable secondary alignment systems, and alignment marks arranged in the16 alignment shot areas on the wafer are detected by the sequenceaccording to the five alignment systems. However, the secondaryalignment system does not need to be movable, and, further, the numberof the secondary alignment systems does not matter. The important thingis that there is at least one alignment system that can detect thealignment marks on the wafer.

Incidentally, in the embodiment above, the exposure apparatus which isequipped with measurement stage MST separately from wafer stage WST wasdescribed as in the exposure apparatus disclosed in the pamphlet ofInternational Publication No. WO 2005/074014, however, the presentinvention is not limited to this, and for example, as is disclosed in,for example, Kokai (Japanese Patent Unexamined Application Publication)No. 10-214783 and the corresponding U.S. Pat. No. 6,341,007, and in thepamphlet of International Publication No. WO 98/40791 and thecorresponding U.S. Pat. No. 6,262,796 and the like, even in an exposureapparatus by the twin wafer stage method that can execute the exposureoperation and the measurement operation (e.g., mark detection by thealignment system) almost in parallel using two wafer stages, it ispossible to perform the position control of each wafer stage the encodersystem (refer to FIG. 3 and the like) previously described. Byappropriately setting the placement and length of each head unit notonly during the exposure operation but also during the measurementoperation, the position control of each wafer stage can be performedcontinuing the use of the encoder system previously described, however,a head unit that can be used during the measurement operation can bearranged, separately from head units (62A to 62D) previously described.For example, four head units can be placed in the shape of a cross withone or two alignment systems in the center, and during the measurementoperation above, the positional information of each wafer stage WST canbe measured using these head units and the corresponding scales. In theexposure apparatus by the twin wafer stage method, at least two scaleseach is arranged in the two wafer stages, respectively, and when theexposure operation of the wafer mounted on one of the wafer stages iscompleted, in exchange with the stage, the other wafer stage on whichthe next wafer that has undergone mark detection and the like at themeasurement position is mounted is placed at the exposure position.Further, the measurement operation performed in parallel with theexposure operation is not limited to the mark detection of wafers andthe like by the alignment system, and instead of this, or in combinationwith this, the surface information (step information) of the wafer canalso be detected.

Incidentally, in the embodiment above, the case has been described whereSec-BCHK (interval) is performed using CD bar 46 on the measurementstage MST side while each wafer is exchanged on the wafer stage WSTside, however, the present invention is not limited to this, and atleast one of an illuminance irregularity measurement (and illuminancemeasurement), aerial image measurement, wavefront aberration measurementand the like can be performed using a measuring instrument (measurementmember) of measurement stage MST, and the measurement results can bereflected in the exposure of the wafer performed later on. To be moreconcrete, for example, projection optical system PL can be adjusted byadjustment unit 68 based on the measurement results.

Further, in the embodiment above, a scale can also be placed onmeasurement stage MST, the position control of the measurement stage canbe performed using the encoder system (head unit) previously described.More specifically, the movable body that performs the measurement ofpositional information using the encoder system is not limited to thewafer stage.

Incidentally, when reducing the size and weight of wafer stage WST istaken into consideration, it is desirable to place the scale as close aspossible to wafer W on wafer stage WST, however, when the size of thewafer stage is allowed to increase, by increasing the size of the waferstage and increasing the distance between the pair of scales that isplaced facing the stage, positional information of at least two each inthe X-axis and Y-axis directions, that is, a total of four positionalinformation, can be measured constantly during the exposure operation.Further, instead of increasing the size of the wafer stage, for example,a part of the scale can be arranged so that it protrudes from the waferstage, or, by placing the scale on the outer side of wafer stage mainbody using an auxiliary plate on which at least one scale is arranged,the distance between the pair of scales that face the stage can beincreased as in the description above.

Further, in the embodiment above, in order to prevent deterioration inthe measurement accuracy caused by adhesion of a foreign material,contamination, and the like to Y scales 39Y₁ and 39Y₂, and X scales 39X₁and 39X₂, for example, a coating can be applied on the surface so as tocover at least the diffraction grating, or a cover glass can bearranged. In this case, especially in the case of a liquid immersiontype exposure apparatus, a liquid repellent protection film can becoated on the scale (a grating surface), or a liquid repellent film canbe formed on the surface (upper surface) of the cover glass.Furthermore, the diffraction grating was formed continually onsubstantially the entire area in the longitudinal direction of eachscale, however, for example, the diffraction grating can be formedintermittently divided into a plurality of areas, or each scale can beconfigured by a plurality of scales. Further, in the embodiment above,an example was given in the case where an encoder by the diffractioninterference method is used as the encoder, however, the presentinvention is not limited to this, and methods such as the so-calledpickup method, the magnetic method and the like can be used, and theso-called scan encoders whose details are disclosed in, for example,U.S. Pat. No. 6,639,686 and the like, can also be used.

Further, in the embodiment above, as the Z sensor, instead of the sensorby the optical pick-up method referred to above, for example, a sensorconfigured by a first sensor (the sensor can be a sensor by the opticalpick-up method or other optical displacement sensors) that projects aprobe beam on a measurement object surface and optically reads thedisplacement of the measurement object surface in the Z-axis directionby receiving the reflected light, a drive section that drives the firstsensor in the Z-axis direction, and a second sensor (e.g. encoders andthe like) that measures the displacement of the first sensor in theZ-axis direction can be used. In the Z sensor having the configurationdescribed above, a mode (the first servo control mode) in which thedrive section drives the first sensor in the Z-axis direction based onthe output of the first sensor so that the distance between themeasurement object surface, such as the surface of the scale and thefirst sensor in the Z-axis direction is always constant, and a mode (thefirst servo control mode) in which a target value of the second sensoris given from an external section (controller) and the drive sectionmaintains the position of the first sensor in the Z-axis direction sothat the measurement values of the second sensor coincides with thetarget value can be set. In the case of the first servo control mode, asthe output of the Z sensor, the output of the measuring section (thesecond sensor) can be used, and in the case of the second servo controlmode, the output of the second sensor can be used. Further, in the caseof using such a Z sensor, and when an encoder is employed as the secondsensor, as a consequence, the positional information of wafer stage WST(wafer table WTB) in directions of six degrees of freedom can bemeasured using an encoder. Further, in the embodiment above, as the Zsensor, a sensor by other detection methods can be employed.

Further, in the embodiment above, the configuration of the plurality ofinterferometers used for measuring the positional information of waferstage WST and their combination are not limited to the configuration andthe combination previously described. The important thing is that aslong as the positional information of wafer stage WST of the directionexcept for the measurement direction of the encoder system can bemeasured, the configuration of the interferometers and their combinationdoes not especially matter. The important thing is that there should bea measurement unit (it does not matter whether it is an interferometeror not) besides the encoder system described above that can measure thepositional information of wafer stage WST in the direction except forthe measurement direction of the encoder system. For example, the Zsensor previously described can be used as such a measurement unit.

Further, in the embodiment above, the Z sensor was arranged besides themultipoint AF system, however, for example, in the case the surfaceposition information of the shot area subject to exposure of wafer W canbe detected with the multipoint AF system on exposure, then the Z sensordoes not necessarily have to be arranged.

Incidentally, in the embodiment above, pure water (water) was used asthe liquid, however, it is a matter of course that the present inventionis not limited to this. As the liquid, liquid that is chemically stable,having high transmittance to illumination light IL and safe to use, suchas a fluorine-containing inert liquid may be used. As thefluorine-containing inert liquid, for example, Fluorinert (the brandname of 3M United States) can be used. The fluorine-containing inertliquid is also excellent from the point of cooling effect. Further, asthe liquid, liquid which has a refractive index higher than pure water(a refractive index is around 1.44), for example, liquid having arefractive index equal to or higher than 1.5 can be used. As this typeof liquid, for example, a predetermined liquid having C—H binding or O—Hbinding such as isopropanol having a refractive index of about 1.50,glycerol (glycerin) having a refractive index of about 1.61, apredetermined liquid (organic solvent) such as hexane, heptane ordecane, or decalin (decahydronaphthalene) having a refractive index ofabout 1.60, or the like can be cited. Alternatively, a liquid obtainedby mixing arbitrary two or more of these liquids may be used, or aliquid obtained by adding (mixing) the predetermined liquid to (with)pure water can be used. Alternatively, as the liquid, a liquid obtainedby adding (mixing) base or acid such as H⁺, Cs⁺, K⁺, Cl⁻, SO₄ ²⁻, or PO₄²⁻ to (with) pure water can be used. Moreover, a liquid obtained byadding (mixing) particles of Al oxide or the like to (with) pure watercan be used. These liquids can transmit ArF excimer laser light.Further, as the liquid, liquid, which has a small absorption coefficientof light, is less temperature-dependent, and is stable to a projectionoptical system (tip optical member) and/or a photosensitive agent (or aprotection film (top coat film), an antireflection film, or the like)coated on the surface of a wafer, is preferable. Further, in the case anF₂ laser is used as the light source, fomblin oil can be selected.

Further, in the embodiment above, the recovered liquid may be reused,and in this case, a filter that removes impurities from the recoveredliquid is preferably arranged in a liquid recovery unit, a recovery pipeor the like.

Further, in the embodiment above, the case has been described where theexposure apparatus is a liquid immersion type exposure apparatus,however, the present invention is not limited to this, and it can alsobe applied to a dry type exposure apparatus that performs exposure ofwafer W without liquid (water).

Further, in the embodiment above, the case has been described where thepresent invention is applied to a scanning exposure apparatus by astep-and-scan method or the like. However, the present invention is notlimited to this, but may also be applied to a static exposure apparatussuch as a stepper. Even with the stepper or the like, by measuring theposition of a stage on which an object subject to exposure is mounted byencoders, generation of position measurement error caused by airfluctuations can substantially be nulled likewise. Further, with thestepper or the like, the switching of the encoder used for positioncontrol of the stage can be performed as is previously described, and acombination of the encoders (heads) subject to the switching can be madeout and the schedule for the switching timing prepared. Further, thetiming of the switching operation can be in synchronization with thetiming of the position control of the stage. Furthermore, it becomespossible to set the position of the stage with high precision based onthe measurement values of the encoder and each of the correctioninformation previously described, and as a consequence, it becomespossible to transfer a reticle pattern onto an object with highprecision. Further, the present invention can also be applied to areduction projection exposure apparatus by a step-and-stitch method thatsynthesizes a shot area and a shot area, an exposure apparatus by aproximity method, a mirror projection aligner, or the like.

Further, the magnification of the projection optical system in theexposure apparatus of the embodiment above is not only a reductionsystem, but can also be either an equal magnifying system or amagnifying system, and projection optical system PL is not only adioptric system, but can also be either a catoptric system or acatadioptric system, and in addition, the projected image may be eitheran inverted image or an upright image. Moreover, the exposure area towhich illumination light IL is irradiated via projection optical systemPL is an on-axis area that includes optical axis AX within the field ofprojection optical system PL. However, for example, as is disclosed inthe pamphlet of International Publication No. WO 2004/107011, theexposure area can also be an off-axis area that does not include opticalaxis AX, similar to a so-called inline type catadioptric system, in partof which an optical system (catoptric system or catadioptric system)that has plural reflection surfaces and forms an intermediate image atleast once is arranged, and which has a single optical axis. Further,the illumination area and exposure area described above are to have arectangular shape. However, the shape is not limited to rectangular, andcan also be circular arc, trapezoidal, parallelogram or the like.

Incidentally, a light source of the exposure apparatus in the embodimentabove is not limited to the ArF excimer laser, but a pulse laser lightsource such as a KrF excimer laser (output wavelength: 248 nm), an F₂laser (output wavelength: 157 nm), an Ar₂ laser (output wavelength: 126nm) or a Kr₂ laser (output wavelength: 146 nm), or an extra-highpressure mercury lamp that generates an emission line such as a g-line(wavelength: 436 nm) or an i-line (wavelength: 365 nm) can also be used.Further, a harmonic wave generating unit of a YAG laser or the like canalso be used. Besides the sources above, as is disclosed in, forexample, the pamphlet of International Publication No. WO 1999/46835(the corresponding U.S. Pat. No. 7,023,610), a harmonic wave, which isobtained by amplifying a single-wavelength laser beam in the infrared orvisible range emitted by a DFB semiconductor laser or fiber laser asvacuum ultraviolet light, with a fiber amplifier doped with, forexample, erbium (or both erbium and ytteribium), and by converting thewavelength into ultraviolet light using a nonlinear optical crystal, canalso be used.

Further, in the embodiment above, illumination light IL of the exposureapparatus is not limited to the light having a wavelength equal to ormore than 100 nm, and it is needless to say that the light having awavelength less than 100 nm can be used. For example, in recent years,in order to expose a pattern equal to or less than 70 nm, development ofan EUV exposure apparatus that makes an SOR or a plasma laser as a lightsource generate an EUV (Extreme Ultraviolet) light in a soft X-ray range(e.g. a wavelength range from 5 to 15 nm), and uses a total reflectionreduction optical system designed under the exposure wavelength (e.g.13.5 nm) and the reflective mask is underway. In the EUV exposureapparatus, the arrangement in which scanning exposure is performed bysynchronously scanning a mask and a wafer using a circular arcillumination can be considered, and therefore, the present invention canalso be suitably applied to such an exposure apparatus. Besides such anapparatus, the present invention can also be applied to an exposureapparatus that uses charged particle beams such as an electron beam oran ion beam.

Further, in the embodiment above, a transmissive type mask (reticle),which is a transmissive substrate on which a predetermined lightshielding pattern (or a phase pattern or a light attenuation pattern) isformed, is used. Instead of this reticle, however, as is disclosed in,for example, U.S. Pat. No. 6,778,257, an electron mask (which is alsocalled a variable shaped mask, an active mask or an image generator, andincludes, for example, a DMD (Digital Micromirror Device) that is a typeof a non-emission type image display device (spatial light modulator) orthe like) on which a light-transmitting pattern, a reflection pattern,or an emission pattern is formed according to electronic data of thepattern that is to be exposed can also be used. In the case of usingsuch a variable shaped mask, because the stage on which a wafer or aglass plate is mounted moves relatively with respect to the variableshaped mask, by driving the stage based on the measurement values of anencoder and each correction information previously described whilemeasuring the position of the stage within the movement plane using theencoder system and performing the linkage operation between a pluralityof encoders previously described, an equivalent effect as the embodimentdescribed above can be obtained.

Further, as is disclosed in, for example, the pamphlet of InternationalPublication No. WO 2001/035168, the present invention can also beapplied to an exposure apparatus (lithography system) that formsline-and-space patterns on a wafer by forming interference fringes onthe wafer.

Moreover, the present invention can also be applied to an exposureapparatus that synthesizes two reticle patterns via a projection opticalsystem and almost simultaneously performs double exposure of one shotarea by one scanning exposure, as is disclosed in, for example, Kohyo(published Japanese translation of International Publication for PatentApplication) No. 2004-519850 (the corresponding U.S. Pat. No.6,611,316).

Further, an apparatus that forms a pattern on an object is not limitedto the exposure apparatus (lithography system) described above, and forexample, the present invention can also be applied to an apparatus thatforms a pattern on an object by an ink-jet method.

Incidentally, an object on which a pattern is to be formed (an objectsubject to exposure to which an energy beam is irradiated) in theembodiment above is not limited to a wafer, and can be other objectssuch as a glass plate, a ceramic substrate, a film member, or a maskblank.

The use of the exposure apparatus is not limited only to the exposureapparatus for manufacturing semiconductor devices, but the presentinvention can also be widely applied to an exposure apparatus fortransferring a liquid crystal display device pattern onto a rectangularglass plate and an exposure apparatus for producing organic ELs,thin-film magnetic heads, imaging devices (such as CCDs), micromachines,DNA chips, and the like. Further, the present invention can be appliednot only to an exposure apparatus for producing microdevices such assemiconductor devices, but can also be applied to an exposure apparatusthat transfers a circuit pattern onto a glass plate or silicon wafer toproduce a mask or reticle used in a light exposure apparatus, an EUVexposure apparatus, an X-ray exposure apparatus, an electron-beamexposure apparatus, and the like.

Incidentally, the movable body drive system, the movable body drivemethod, or the deciding method of the present invention can be appliednot only to the exposure apparatus, but can also be applied widely toother substrate processing apparatuses (such as a laser repairapparatus, a substrate inspection apparatus and the like), or toapparatuses equipped with a movable body such as a stage that moveswithin a two-dimensional plane such as a position setting apparatus forsamples or a wire bonding apparatus in other precision machines.

Further, the exposure apparatus (the pattern forming apparatus) of theembodiment above is manufactured by assembling various subsystems, whichinclude the respective constituents that are recited in the claims ofthe present application, so as to keep predetermined mechanicalaccuracy, electrical accuracy and optical accuracy. In order to securethese various kinds of accuracy, before and after the assembly,adjustment to achieve the optical accuracy for various optical systems,adjustment to achieve the mechanical accuracy for various mechanicalsystems, and adjustment to achieve the electrical accuracy for variouselectric systems are performed. A process of assembling varioussubsystems into the exposure apparatus includes mechanical connection,wiring connection of electric circuits, piping connection of pressurecircuits, and the like among various types of subsystems. Needless tosay, an assembly process of individual subsystem is performed before theprocess of assembling the various subsystems into the exposureapparatus. When the process of assembling the various subsystems intothe exposure apparatus is completed, a total adjustment is performed andvarious kinds of accuracy as the entire exposure apparatus are secured.Incidentally, the making of the exposure apparatus is preferablyperformed in a clean room where the temperature, the degree ofcleanliness and the like are controlled.

Incidentally, the disclosures of the various publications, the pamphletsof the International Publications, and the U.S. patent applicationPublication descriptions and the U.S. patent descriptions that are citedin the embodiment above and related to exposure apparatuses and the likeare each incorporated herein by reference.

Next, an embodiment of a device manufacturing method in which theexposure apparatus (pattern forming apparatus) described above is usedin a lithography process will be described.

FIG. 41 shows a flowchart of an example when manufacturing a device (asemiconductor chip such as an IC or an LSI, a liquid crystal panel, aCCD, a thin film magnetic head, a micromachine, and the like). As isshown in FIG. 41, first of all, in step 201 (design step), function andperformance design of device (such as circuit design of semiconductordevice) is performed, and pattern design to realize the function isperformed. Then, in step 202 (a mask making step), a mask (reticle) ismade on which the circuit pattern that has been designed is formed.Meanwhile, in step 203 (a wafer fabrication step), wafers aremanufactured using materials such as silicon.

Next, in step 204 (wafer processing step), the actual circuit and thelike are formed on the wafer by lithography or the like in a manner thatwill be described later, using the mask and the wafer prepared in steps201 to 203. Then, in step 205 (device assembly step), device assembly isperformed using the wafer processed in step 204. Step 205 includesprocesses such as the dicing process, the bonding process, and thepackaging process (chip encapsulation), and the like when necessary.

Finally, in step 206 (an inspecting step), tests are performed on adevice made in step 205, such as the operation check test, durabilitytest and the like. After these processes, the devices are completed andare shipped out.

FIG. 42 is a flowchart showing a detailed example of step 204 describedabove. In FIG. 42, in step 211 (an oxidation step), the surface of waferis oxidized. In step 212 (CDV step), an insulating film is formed on thewafer surface. In step 213 (an electrode formation step), an electrodeis formed on the wafer by deposition. In step 214 (an ion implantationstep), ions are implanted into the wafer. Each of the above steps 211 tostep 214 constitutes the preprocess in each step of wafer processing,and the necessary processing is chosen and is executed at each stage.

When the above-described preprocess ends in each stage of waferprocessing, post-process is executed as follows. First of all, in thepost-process, first in step 215 (a resist formation step), aphotosensitive agent is coated on the wafer. Then, in step 216 (exposurestep), the circuit pattern of the mask is transferred onto the wafer bythe exposure apparatus (pattern forming apparatus) described above andthe exposure method (pattern forming method) thereof. Next, in step 217(development step), the wafer that has been exposed is developed, and instep 218 (etching step), an exposed member of an area other than thearea where resist remains is removed by etching. Then, in step 219(resist removing step), when etching is completed, the resist that is nolonger necessary is removed.

By repeatedly performing the pre-process and the post-process, multiplecircuit patterns are formed on the wafer.

By using the device manufacturing method of the embodiment describedabove, because the exposure apparatus (pattern forming apparatus) in theembodiment above and the exposure method (pattern forming method)thereof are used in the exposure step (step 216), exposure with highthroughput can be performed while maintaining the high overlay accuracy.Accordingly, the productivity of highly integrated microdevices on whichfine patterns are formed can be improved.

While the above-described embodiments of the present invention are thepresently preferred embodiments thereof, those skilled in the art oflithography systems will readily recognize that numerous additions,modifications, and substitutions may be made to the above-describedembodiments without departing from the spirit and scope thereof. It isintended that all such modifications, additions, and substitutions fallwithin the scope of the present invention, which is best defined by theclaims appended below.

What is claimed is:
 1. An exposure apparatus that exposes a substratevia a projection optical system, the apparatus comprising: a stagesystem having a stage that holds the substrate and a motor coupled tothe stage, that drives the stage by the motor; an encoder system inwhich one of a grating section and a plurality of heads that eachirradiate the grating section with a beam is arranged at the stage, andwhich measures positional information of the stage by a head that facesthe grating section, of the plurality of heads; and a controller thatswitches a head used in measurement of the positional information to adifferent head of the plurality of heads and determines the positionalinformation to be measured by the different head based on the positionalinformation measured by the head used before the switching, duringdriving of the stage based on the measured positional information,wherein after the switching, the measurement by the different head isperformed using the determined positional information.
 2. The exposureapparatus according to claim 1, wherein the positional information to bemeasured by the different head is determined while a head used beforethe switching and a head to be used after the switching both face thegrating section.
 3. The exposure apparatus according to claim 2, whereinthe positional information to be measured by the different head isdetermined on the switching.
 4. The exposure apparatus according toclaim 1, wherein the switching is performed while a head used before theswitching and a head to be used after the switching both face thegrating section.
 5. The exposure apparatus according to claim 1, whereinthe determination and the switching are performed while a head usedbefore the switching and the different head face the grating section. 6.The exposure apparatus according to claim 1, wherein the grating sectionincludes four scales in each of which a grating is formed, before theswitching, the measurement by the heads that face at least three of thefour scales, respectively, is performed, and based on the positionalinformation measured by the at least three heads, the positionalinformation to be measured by the different head that is different fromthe at least three heads is determined.
 7. The exposure apparatusaccording to claim 6, wherein while the at least three heads and thedifferent head face the grating section, the positional information tobe measured by the different head is determined and one of the at leastthree heads is switched to the different head, and after the switching,the measurement by at least three heads including the different headthat face at least three of the four scales, respectively, is performed.8. The exposure apparatus according to claim 1, further comprising: anozzle unit arranged surrounding a lower end portion of the projectionoptical system, and having a recovery port on a lower surface side towhich the stage is placed facing, wherein a liquid immersion area isformed under the projection optical system by a liquid supplied via thenozzle unit, and the substrate is located facing the projection opticalsystem by the stage, and is exposed via the projection optical systemand the liquid of the liquid immersion area.
 9. The exposure apparatusaccording to claim 8, wherein the other of the grating section and theplurality of heads is arranged on an outer side of the nozzle unit withrespect to the projection optical system.
 10. The exposure apparatusaccording to claim 1, wherein the encoder system measures positionalinformation of the stage at least in directions of three degrees offreedom including a direction parallel to a predetermined planeorthogonal to an optical axis of the projection optical system, beforeand after the switching each, the measurement by three or four headsthat face the grating section is performed, and the number of the headsthat face the grating section during the driving of the stage is changedfrom one of three and four to the other.
 11. The exposure apparatusaccording to claim 10, wherein the positional information to be measuredby the different head is determined so that a position of the stage ismaintained before and after the switching or positional information ofthe stage continuously links before and after the switching.
 12. Theexposure apparatus according to claim 10, wherein positional informationof the stage in a direction different from the direction parallel to thepredetermined plane is used to determine the positional information tobe measured by the different head.
 13. The exposure apparatus accordingto claim 10, wherein the controller uses information related to aposition of the head in the driving of the stage.
 14. The exposureapparatus according to claim 10, wherein the controller controls thedriving of the stage based on correction information used to compensatea measurement error of the encoder system that occurs due to at leastone of the grating section and the head.
 15. The exposure apparatusaccording to claim 14, wherein at least one of a measurement error ofthe encoder system that occurs due to at least one of a displacement andan optical property of the head, a measurement error of the encodersystem that occurs due to at least one of flatness and a formation errorof the grating section, and a measurement error of the encoder systemthat occurs due to a displacement of the stage in a direction differentfrom the direction parallel to the predetermined plane on thedetermination is compensated.
 16. The exposure apparatus according toclaim 15, wherein the different direction includes at least one of adirection orthogonal to the predetermined plane, a rotational directionaround an axis orthogonal to the predetermined plane and a rotationaldirection around an axis parallel to the predetermined plane.
 17. Theexposure apparatus according to claim 14, wherein a measurement error ofthe encoder system that occurs due to one of a tilt and a rotation ofthe stage is compensated.
 18. The exposure apparatus according to claim14, wherein one of measurement information of the encoder system and atarget position at which the stage is positioned is corrected based onthe correction information.
 19. The exposure apparatus according toclaim 14, wherein an object is exposed with an energy beam via a mask,and on the exposure, while the stage is driven based on measurementinformation of the encoder system, a position of the mask is controlledbased on the correction information so that the measurement error iscompensated.
 20. A device manufacturing method, including exposing asubstrate using the exposure apparatus according to claim 1; anddeveloping the substrate that has been exposed.
 21. An exposure methodof exposing a substrate via a projection optical system, the methodcomprising: measuring positional information of a stage that holds thesubstrate by a head that faces a grating section, of a plurality ofheads in an encoder system, one of the grating section and the pluralityof heads being arranged at the stage, and the plurality of heads eachirradiating the grating section with a beam; and switching a head usedin measurement of the positional information to a different head, of theplurality of heads, during driving of the stage based on the measuredpositional information, wherein for the switching, the positionalinformation to be measured by the different head is determined based onthe positional information measured by the head used before theswitching, and after the switching, the measurement by the differenthead is performed using the determined positional information.
 22. Theexposure method according to claim 21, wherein the positionalinformation to be measured by the different head is determined while ahead used before the switching and a head to be used after the switchingboth face the grating section.
 23. The exposure method according toclaim 22, wherein the positional information to be measured by thedifferent head is determined on the switching.
 24. The exposure methodaccording to claim 21, wherein the switching is performed while a headused before the switching and a head to be used after the switching bothface the grating section.
 25. The exposure method according to claim 21,wherein the determination and the switching are performed while a headused before the switching and the different head face the gratingsection.
 26. The exposure method according to claim 21, wherein thegrating section includes four scales in each of which a grating isformed, before the switching, the measurement by the heads that face atleast three of the four scales, respectively, is performed, and based onthe positional information measured by the at least three heads, thepositional information to be measured by the different head that isdifferent from the at least three heads is determined.
 27. The exposuremethod according to claim 26, wherein while the at least three heads andthe different head face the grating section, the positional informationto be measured by the different head is determined and one of the atleast three heads is switched to the different head, and after theswitching, the measurement by at least three heads including thedifferent head that face at least three of the four scales,respectively, is performed.
 28. The exposure method according to claim21, wherein a liquid immersion area is formed under the projectionoptical system by a liquid supplied via a nozzle unit that is arrangedsurrounding a lower end portion of the projection optical system and hasa recovery port on a lower surface side to which the stage is placedfacing, and the substrate is located facing the projection opticalsystem by the stage, and is exposed via the projection optical systemand the liquid of the liquid immersion area.
 29. The exposure methodaccording to claim 28, wherein the other of the grating section and theplurality of heads is arranged on an outer side of the nozzle unit withrespect to the projection optical system.
 30. The exposure methodaccording to claim 21, wherein the encoder system measures positionalinformation of the stage at least in directions of three degrees offreedom including a direction parallel to a predetermined planeorthogonal to an optical axis of the projection optical system, beforeand after the switching each, the measurement by three or four headsthat face the grating section is performed, and the number of the headsthat face the grating section during the driving of the stage is changedfrom one of three and four to the other.
 31. The exposure methodaccording to claim 30, wherein the positional information to be measuredby the different head is determined so that a position of the stage ismaintained before and after the switching or positional information ofthe stage continuously links before and after the switching.
 32. Theexposure method according to claim 30, wherein positional information ofthe stage in a direction different from the direction parallel to thepredetermined plane is used to determine the positional information tobe measured by the different head.
 33. The exposure method according toclaim 30, wherein information related to a position of the head is usedin the driving of the stage.
 34. The exposure method according to claim30, wherein the driving of the stage is controlled based on correctioninformation used to compensate a measurement error of the encoder systemthat occurs due to at least one of the grating section and the head. 35.The exposure method according to claim 34, wherein at least one of ameasurement error of the encoder system that occurs due to at least oneof a displacement and an optical property of the head, a measurementerror of the encoder system that occurs due to at least one of flatnessand a formation error of the grating section, and a measurement error ofthe encoder system that occurs due to a displacement of the stage in adirection different from the direction parallel to the predeterminedplane on the determination is compensated.
 36. The exposure methodaccording to claim 35, wherein the different direction includes at leastone of a direction orthogonal to the predetermined plane, a rotationaldirection around an axis orthogonal to the predetermined plane and arotational direction around an axis parallel to the predetermined plane.37. The exposure method according to claim 34, wherein a measurementerror of the encoder system that occurs due to one of a tilt and arotation of the stage is compensated.
 38. The exposure method accordingto claim 34, wherein one of measurement information of the encodersystem and a target position at which the stage is positioned iscorrected based on the correction information.
 39. The exposure methodaccording to claim 34, wherein an object is exposed with an energy beamvia a mask, and on the exposure, while the stage is driven based onmeasurement information of the encoder system, a position of the mask iscontrolled based on the correction information so that the measurementerror is compensated.
 40. A device manufacturing method, includingexposing a substrate using the exposure method according to claim 21;and developing the substrate that has been exposed.
 41. An exposuremethod of exposing a substrate via a projection optical system, themethod comprising: a first process of measuring positional informationof a stage that holds the substrate by a head that faces a gratingsection, of a plurality of heads in an encoder system, one of thegrating section and the plurality of heads being arranged at the stage,and the plurality of heads each irradiating the grating section with abeam; a second process of switching a head used in measurement of thepositional information to a different head, of the plurality of heads,during driving of the stage based on the measured positionalinformation; and a third process of measuring positional information ofthe stage by the different head that has been switched to, wherein inthe second process, the positional information to be measured by thedifferent head is determined based on the positional informationmeasured by the head in operation in the first process, and in the thirdprocess, the measurement by the different head is performed using thedetermined positional information.
 42. The exposure method according toclaim 41, wherein the positional information to be measured by thedifferent head is determined and switching of the head is performed,while a head used before the switching and a head to be used after theswitching both face the grating section.
 43. A device manufacturingmethod, including exposing a substrate using the exposure methodaccording to claim 42; and developing the substrate that has beenexposed.
 44. A method of making an exposure apparatus that exposes asubstrate via a projection optical system, the method comprising:providing a stage system having a stage that holds the substrate and amotor coupled to the stage, that drives the stage by the motor;providing an encoder system in which one of a grating section and aplurality of heads that each irradiate the grating section with a beamis arranged at the stage, and which measures positional information ofthe stage by a head that faces the grating section, of the plurality ofheads; and providing a controller that switches a head used inmeasurement of the positional information to a different head of theplurality of heads and determines the positional information to bemeasured by the different head based on the positional informationmeasured by the head used before the switching, during driving of thestage based on the measured positional information, wherein after theswitching, the measurement by the different head is performed using thedetermined positional information.